Resist composition and resist pattern forming method

ABSTRACT

A resist composition which generates an acid upon exposure and exhibits changed solubility in a developing solution by the action of the acid contains a high-molecular weight compound (A1) having a constituent unit (a0) represented by a general formula (a0-1) and a constituent unit (a1-1) including a monocyclic group-containing acid decomposable group whose polarity increases by the action of an acid. In the formula (a0-1), R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms; Ya 01  represents a single bond or a divalent linking group; X 01  represents a sulfur atom or an oxygen atom; and Ra 01  represents an optionally substituted cyclic group, chain alkyl group, or chain alkenyl group.

CROSS-REFERENCE TO RELATED APPLICATIONS

Priority is claimed on Japanese Patent Application No. 2013-062866,filed Mar. 25, 2013, the content of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a resist composition and a resistpattern forming method.

2. Background Art

In lithography techniques, for example, a process including forming aresist film formed of a resist material on a substrate, performingselective exposure on the resist film, and performing a developmenttreatment, thereby forming a resist pattern having a predetermined shapeon the resist film is performed. A resist material whose characteristicsare changed so that the exposed areas of the resist film are dissolvedin a developing solution is referred to as a positive type, and a resistmaterial whose characteristics are changed so that the exposed areas arenot dissolved in a developing solution is referred to as a negativetype.

In recent years, in the manufacturing of semiconductor elements andliquid crystal display elements, advances in lithography technologieshave led to rapid progress in the field of pattern miniaturization. Ingeneral, these miniaturization techniques involve shortening of thewavelength (increasing the energy) of the exposure light source.Specifically, ultraviolet rays represented by g-line or i-line havehitherto been used. But nowadays, KrF excimer lasers and ArF excimerlasers are starting to be introduced in mass production ofsemiconductors. In addition, investigations are also being conducted onEUV (extreme ultraviolet radiation), EB (electron beams), X-rays, andthe like, which have a shorter wavelength (higher energy) than theseexcimer lasers.

The resist material is required to have lithography properties such assensitivity to the exposure light source and resolution capable ofreproducing patterns of minute dimensions.

As the resist material that satisfies such requirements, a chemicallyamplified resist composition containing a base material component whichexhibits changed solubility in a developing solution by the action of anacid and an acid generator component that generates an acid uponexposure has been used.

For example, in the case where the developing solution is an alkalideveloping solution (alkali development process), a compositioncontaining a resin component (base resin) exhibiting increasedsolubility in the alkali developing solution by the action of an acidand an acid generator component is generally used as a positive-typechemically amplified resist composition. When a resist film formed usingsuch a resist composition is selectively exposed during the formation ofa resist pattern, an acid is generated from the acid generator componentin the exposed areas, the polarity of the base resin increases by theaction of the acid, and thus the exposed areas become soluble in thealkali developing solution. Therefore, alkali development is performedto form a positive type pattern in which the unexposed areas remain as apattern.

When such a chemically amplified resist composition is applied to asolvent development process using a developing solution (organicdeveloping solution) containing an organic solvent, the solubility in anorganic developing solution relatively decreases as the polarity of thebase resin increases. Thus, the unexposed areas of the resist film aredissolved and removed by the organic developing solution and a negativetype resist pattern in which the exposed areas remain as a pattern isformed. The solvent development process adapted to form a negative typeresist pattern as described above is sometimes referred to as a negativetype development process (see, for example, JP-A-2009-025723).

In general, the base resin used in the chemically amplified resistcomposition has plural kinds of constituent units for the purpose ofenhancing lithography properties and the like.

For example, in the case of a resin component which exhibits increasedsolubility in an alkali developing solution by the action of an acid, aconstituent unit including an acid decomposable group which isdecomposed by the action of an acid generated from an acid generator toincrease its polarity is used. In addition, a constituent unit includinga lactone-containing cyclic group, a constituent unit including a polargroup such as a hydroxyl group, and the like are used in combination(see, for example, JP-A-2003-241365).

Recently, a demand for a high-molecular weight compound which is usefulas a base resin for a resist composition has increased with gradualprogress in the field of pattern miniaturization.

For example, in order to improve roughness, a resist composition using ahigh-molecular weight compound having a constituent unit including amonocyclic group-containing acid decomposable group as theabove-described acid decomposable group is proposed (seeJP-A-2008-003381).

SUMMARY OF THE INVENTION

While lithography techniques advance and application fields thereof areexpanded, enhancements of various lithography properties such as anincrease of sensitivity and an improvement of roughness in the formationof a resist pattern are required. However, for example, in the case ofthe resist composition described in JP-A-2008-003381, it was difficultto secure a sufficient thickness (pattern height) of a resist film afterdevelopment.

The invention is contrived in view of the circumstances, and an objectthereof is to provide a resist composition which can form a resistpattern which is excellent in various lithography properties.

According to a first aspect of the invention, there is provided a resistcomposition which generates an acid upon exposure and exhibits changedsolubility in a developing solution by the action of the acid, includinga base material component (A) which exhibits changed solubility in adeveloping solution by the action of an acid, in which the base materialcomponent (A) contains a high-molecular weight compound (A1) having aconstituent unit (a0) represented by the following general formula(a0-1) and a constituent unit (a1-1) including a monocyclicgroup-containing acid decomposable group whose polarity increases by theaction of an acid.

In the formula, R represents a hydrogen atom, an alkyl group having 1 to5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms;Ya⁰¹ a single bond or a divalent linking group; X⁰¹ represents a sulfuratom or an oxygen atom; and Ra⁰¹ represents an optionally substitutedcyclic group, an optionally substituted chain alkyl group, or anoptionally substituted chain alkenyl group.

According to a second aspect of the invention, there is provided aresist pattern forming method including: forming a resist film on asupport using the resist composition of the first aspect of theinvention; exposing the resist film; and developing the resist filmafter the exposure to form a resist pattern.

According to a resist composition and a resist pattern forming method ofthe invention, it is possible to form a resist pattern which isexcellent in various lithography properties.

DETAILED DESCRIPTION OF THE INVENTION

In the present specification and claims, the term “aliphatic” is arelative concept used in relation to the term “aromatic” and defines agroup or a compound each having no aromaticity.

The term “alkyl group” includes a linear, branched or cyclic, monovalentsaturated hydrocarbon group, unless otherwise specified. The sameapplies for the alkyl group within an alkoxy group.

The term “alkylene group” includes a linear, branched or cyclic,divalent saturated hydrocarbon group, unless otherwise specified.

The term “halogenated alkyl group” refers to a group in which some orall hydrogen atoms of an alkyl group are substituted with a halogenatom. Examples of the halogen atom include a fluorine atom, a chlorineatom, a bromine atom, and an iodine atom.

The term “fluorinated alkyl group” or “fluorinated alkylene group”refers to a group in which some or all hydrogen atoms of an alkyl groupor an alkylene group are substituted with a fluorine atom.

The term “constituent unit” means a monomer unit constituting ahigh-molecular weight compound (for example, a resin, a polymer, or acopolymer).

The case of describing “may have a substituent” or “optionallysubstituted” includes both of the case where the hydrogen atom (—H) issubstituted with a monovalent group and the case where the methylenegroup (—CH₂—) is substituted with a divalent group.

The term “exposure” is a concept including irradiation with any form ofradiation.

The term “constituent unit derived from an acrylic ester” means aconstituent unit constituted upon cleavage of an ethylenic double bondof an acrylic ester.

The term “acrylic ester” refers to a compound in which a terminalhydrogen atom of a carboxy group of acrylic acid (CH₂═CH—COOH) issubstituted with an organic group.

In the acrylic ester, a hydrogen atom bonded to a carbon atom at theα-position may be substituted with a substituent. The substituent(R^(α0)) with which the hydrogen atom bonded to the carbon atom at theα-position is substituted is an atom other than the hydrogen atom or agroup, and examples thereof include an alkyl group having 1 to 5 carbonatoms and a halogenated alkyl group having 1 to 5 carbon atoms. Inaddition, examples of the acrylic ester also include an itaconic aciddiester in which the substituent (R^(α0)) is substituted with an esterbond-containing substituent and an α-hydroxyacrylic ester in which thesubstituent (R^(α0)) is substituted with a hydroxyalkyl group or a groupin which the hydroxyl group of the hydroxyalkyl group is modified. It isto be noted that the carbon atom at the α-position of the acrylic esterrefers to a carbon atom to which the carbonyl group of acrylic acid isbonded, unless otherwise specified.

The acrylic ester in which the hydrogen atom bonded to the carbon atomat the α-position is substituted with a substituent is hereinaftersometimes referred to as “α-substituted acrylic ester”. In addition, theacrylic ester and the α-substituted acrylic ester are sometimes referredto comprehensively as “(α-substituted) acrylic ester”.

The term “constituent unit derived from acrylamide” means a constituentunit constituted upon cleavage of an ethylenic double bond ofacrylamide.

In the acrylamide, the hydrogen atom bonded to the carbon atom at theα-position may be substituted with a substituent, and either one or bothof the hydrogen atoms of the amino group of the acrylamide may besubstituted with a substituent. It is to be noted that the carbon atomat the α-position of the acrylamide refers to a carbon atom to which thecarbonyl group of the acrylamide is bonded, unless otherwise specified.

Examples of the substituent with which the hydrogen atom bonded to thecarbon atom at the α-position of the acrylamide is substituted includethose exemplified above as the substituent at the α-position(substituent) (R^(α0))) for the α-substituted acrylic ester.

The term “constituent unit derived from hydroxystyrene or ahydroxystyrene derivative” means a constituent unit constituted uponcleavage of an ethylenic double bond of hydroxystyrene or ahydroxystyrene derivative.

The term “hydroxystyrene derivative” is a concept including compounds inwhich the hydrogen atom at the α-position of hydroxystyrene issubstituted with other substituent such as an alkyl group and ahalogenated alkyl group, and derivatives thereof. Examples of suchderivatives include those in which the hydrogen atom of the hydroxylgroup of hydroxystyrene in which the hydrogen atom at the α-position maybe substituted with a substituent is substituted with an organic group;and those in which a substituent other than the hydroxyl group is bondedto the benzene ring of hydroxystyrene in which the hydrogen atom at theα-position may be substituted with a substituent. It is to be noted thatthe term “α-position (carbon atom at the α-position)” refers to a carbonatom to which the benzene ring is bonded, unless otherwise specified.

Examples of the substituent with which the hydrogen atom at theα-position of hydroxystyrene is substituted include those exemplifiedabove as the substituent at the α-position for the α-substituted acrylicester.

The term “constituent unit derived from vinylbenzoic acid or avinylbenzoic acid derivative” means a constituent unit constituted uponcleavage of an ethylenic double bond of vinylbenzoic acid or avinylbenzoic acid derivative.

The term “vinylbenzoic acid derivative” is a concept including compoundsin which the hydrogen atom at the α-position of vinylbenzoic acid issubstituted with other substituent such as an alkyl group and ahalogenated alkyl group, and derivatives thereof. Examples of suchderivatives include those in which the hydrogen atom of the carboxygroup of vinylbenzoic acid in which the hydrogen atom at the α-positionmay be substituted with a substituent is substituted with an organicgroup; and those in which a substituent other than a hydroxyl group anda carboxy group is bonded to the benzene ring of vinylbenzoic acid inwhich the hydrogen atom at the α-position may be substituted with asubstituent. It is to be noted that the term “α-position (carbon atom atthe α-position)” refers to a carbon atom to which the benzene ring isbonded, unless otherwise specified.

The term “styrene” is a concept including styrene and compounds in whichthe hydrogen atom at the α-position of styrene is substituted with othersubstituent such as an alkyl group and a halogenated alkyl group.

The term “constituent unit derived from styrene” or “constituent unitderived from a styrene derivative” means a constituent unit constitutedupon cleavage of an ethylenic double bond of styrene or a styrenederivative.

The alkyl group as the substituent at the α-position is preferably alinear or branched alkyl group. Specifically, examples thereof includean alkyl group having 1 to 5 carbon atoms (for example, a methyl group,an ethyl group, a propyl group, an isopropyl group, an n-butyl group, anisobutyl group, a tert-butyl group, a pentyl group, an isopentyl group,or a neopentyl group).

In addition, specifically, examples of the halogenated alkyl group asthe substituent at the α-position include a group in which some or allhydrogen atoms of the above-described “alkyl group as the substituent atthe α-position” are substituted with a halogen atom. Examples of thehalogen atom include a fluorine atom, a chlorine atom, a bromine atom,and an iodine atom, with a fluorine atom being especially preferable.

In addition, specifically, examples of the hydroxyalkyl group as thesubstituent at the α-position include a group in which some or allhydrogen atoms of the above-described “alkyl group as the substituent atthe α-position” are substituted with a hydroxyl group. The number of thehydroxyl group in the hydroxyalkyl group is preferably 1 to 5, and mostpreferably 1.

Resist Composition

A resist composition of a first aspect of the invention is a resistcomposition which generates an acid upon exposure and exhibits changedsolubility in a developing solution by the action of the acid, andcontains a base material component (A) (hereinafter, also referred to as“component (A)”) which exhibits changed solubility in a developingsolution by the action of an acid.

When a resist film is formed using such a resist composition and isselectively exposed, an acid is generated in the exposed areas and thesolubility of the component (A) in the developing solution changes bythe action of the acid, whereas the solubility of the component (A) inthe developing solution does not change in the unexposed areas. Thus, adifference is caused between the exposed areas and the unexposed areasin solubility in the developing solution. Therefore, when the resistfilm is developed, the exposed areas are dissolved and removed and apositive type resist pattern is formed in the case where the resistcomposition is a positive type. In the case where the resist compositionis a negative type, the unexposed areas are dissolved and removed and anegative type resist pattern is formed.

In the present specification, the resist composition which is used toform a positive type resist pattern by dissolving and removing exposedareas is referred to as a positive type resist composition, and theresist composition which is used to form a negative type resist patternby dissolving and removing unexposed areas is referred to as a negativetype resist composition.

The resist composition of this aspect may be a positive type resistcomposition, or a negative type resist composition.

In addition, the resist composition of this aspect may be for use in analkali development process using an alkali developing solution in adevelopment treatment for the case where a resist pattern is formed, orin a solvent development process using a developing solution containingan organic solvent (organic developing solution) in the developmenttreatment.

The resist composition of this aspect has acid generating ability togenerate an acid upon exposure, and the acid may be generated uponexposure from the component (A) or an additive component blendedseparately from the component (A).

Specifically, the resist composition of this aspect may be:

(1) a composition which contains an acid generator component (B) whichgenerates an acid upon exposure (hereinafter, referred to as “component(B)”);

(2) a composition in which the component (A) generates an acid uponexposure; or

(3) a composition in which the component (A) generates an acid uponexposure, and which further contains a component (B).

That is, in the cases of the above-described (2) and (3), the component(A) is a “base material component which generates an acid upon exposureand exhibits changed solubility in a developing solution by the actionof the acid”. When the component (A) is a base material component whichgenerates an acid upon exposure and exhibits changed solubility in adeveloping solution by the action of the acid, a component (A1) to bedescribed later is preferably a high-molecular weight compound whichgenerates an acid upon exposure and exhibits changed solubility in adeveloping solution by the action of the acid. As such a high-molecularweight compound, a resin having a constituent unit which generates anacid upon exposure can be used. A known constituent unit can be used asthe constituent unit which generates an acid upon exposure.

The resist composition of this aspect is preferably the compositiondescribed in (1).

Component (A)

In the invention, the term “base material component” refers to anorganic compound having film-forming ability and an organic compoundpreferably having a molecular weight of 500 or more is used. When themolecular weight of the organic compound is 500 or more, thefilm-forming ability is improved and a nano-level resist pattern iseasily formed.

The organic compound which is used as the base material component isroughly classified into a non-polymerized material and a polymer.

In general, the non-polymerized material has a molecular weight of 500to less than 4,000. Hereinafter, the term “low-molecular weightcompound” refers to a non-polymerized material having a molecular weightof 500 to less than 4,000.

In general, the polymer has a molecular weight of 1,000 or more.Hereinafter, the term “resin” or “high-molecular weight compound” refersto a polymer having a molecular weight of 1,000 or more.

A mass average molecular weight as converted into polystyrene by meansof gel permeation chromatography (GPC) is employed for the molecularweight of the polymer.

The component (A) which is used in the resist composition of this aspectcontains a high-molecular weight compound (A1) (hereinafter, referred toas “component (A1)”) having a constituent unit (a0) represented by ageneral formula (a0-1) and a constituent unit (a1-1) including amonocyclic group-containing acid decomposable group whose polarityincreases by the action of an acid.

At least the component (A1) is used as the component (A), and with thecomponent (A1), other high-molecular weight compounds and/orlow-molecular weight compounds may be used in combination.

Component (A1)

The component (A1) is a high-molecular weight compound having aconstituent unit (a0) represented by a general formula (a0-1) and aconstituent unit (a1-1) including a monocyclic group-containing aciddecomposable group whose polarity increases by the action of an acid.

When a resist film formed using the resist composition of this aspect isexposed, at least a part of the bond in the structure of the constituentunit (a1-1) is cleaved by the action of an acid and the polarity of theconstituent unit increases. Therefore, the resist composition of thisaspect becomes a positive type in an alkali development process, andbecomes a negative type in a solvent development process. The polarityof the component (A1) changes before and after exposure, and thus a gooddevelopment contrast can be obtained using the component (A1) not onlyin the alkali development process, but also in the solvent developmentprocess.

That is, in the case of applying an alkali development process, thecomponent (A1) is sparingly soluble in an alkali developing solutionbefore exposure, but when an acid is generated upon exposure, the actionof the acid causes an increase in polarity, thereby increasing thesolubility in the alkali developing solution. Therefore, in theformation of a resist pattern, by performing selective exposure of aresist film obtained by applying the resist composition to a support,the exposed areas change to have soluble properties from sparinglysoluble properties in the alkali developing solution, whereas theunexposed areas do not change in the state where they are stillsparingly alkali-soluble, and hence, a positive type resist pattern canbe formed by alkali developing.

Meanwhile, in the case of applying a solvent development process, thecomponent (A1) exhibits high solubility in an organic developingsolution before exposure, and when an acid is generated upon exposure,the polarity increases by the action of the acid, thereby decreasing thesolubility in the organic developing solution. Therefore, in theformation of a resist pattern, by performing selective exposure of aresist film obtained by applying the resist composition to a support,the exposed areas change to have sparingly soluble properties fromsoluble properties in the organic developing solution, whereas theunexposed areas do not change in the state where they are still soluble.Thus, a contrast can be made between the exposed areas and unexposedareas by performing developing with the organic developing solution, andthus a negative type resist pattern can be formed.

Constituent Unit (a0)

The constituent unit (a0) is a constituent unit represented by thefollowing general formula (a0-1).

In the formula, R represents a hydrogen atom, an alkyl group having 1 to5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms;Ya⁰¹ represents a single bond or a divalent linking group; X⁰¹represents a sulfur atom or an oxygen atom; and Ra⁰¹ represents anoptionally substituted cyclic group, an optionally substituted chainalkyl group, or an optionally substituted chain alkenyl group.

In the formula (a0-1), the alkyl group having 1 to 5 carbon atoms in Ris preferably a linear or branched alkyl group having 1 to 5 carbonatoms. Specifically, examples thereof include a methyl group, an ethylgroup, a propyl group, an isopropyl group, an n-butyl group, an isobutylgroup, a tert-butyl group, a pentyl group, an isopentyl group, and aneopentyl group.

The halogenated alkyl group having 1 to 5 carbon atoms is a group inwhich some or all the hydrogen atoms of the above-described “alkyl grouphaving 1 to 5 carbon atoms in R” are substituted with halogen atoms.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom, and an iodine atom, and a fluorine atom is especiallypreferable.

R is preferably a hydrogen atom, an alkyl group having 1 to 5 carbonatoms, or a fluorinated alkyl group having 1 to 5 carbon atoms, and isespecially preferably a hydrogen atom or a methyl group in terms ofeasiness in industrial availability.

In the formula (a0-1), Ya⁰¹ represents a single bond or a divalentlinking group.

The divalent linking group in Ya⁰¹ is not particularly limited, andpreferred examples thereof include an optionally substituted divalenthydrocarbon group and a hetero atom-containing divalent linking group.

Optionally Substituted Divalent Hydrocarbon Group:

When Ya⁰¹ represents an optionally substituted divalent hydrocarbongroup, the hydrocarbon group may be an aliphatic hydrocarbon group or anaromatic hydrocarbon group.

Aliphatic Hydrocarbon Group in Ya⁰¹

The aliphatic hydrocarbon group means a hydrocarbon group having noaromaticity. The aliphatic hydrocarbon group may be either saturated orunsaturated, and in general, it is preferably saturated.

Examples of the aliphatic hydrocarbon group include a linear or branchedaliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in a structure thereof.

Linear or Branched Aliphatic Hydrocarbon Group

The linear or branched aliphatic hydrocarbon group preferably has 1 to10 carbon atoms, more preferably 1 to 6 carbon atoms, still morepreferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbon atoms.

The linear aliphatic hydrocarbon group is preferably a linear alkylenegroup, and specifically, examples thereof include a methylene group[—CH₂—], an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—],a tetramethylene group [—(CH₂)₄—], and a pentamethylene group[—(CH₂)₅—].

The branched aliphatic hydrocarbon group is preferably a branchedalkylene group, and specifically, examples thereof include alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH)CH₂CH₂CH₂— and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group in the alkylalkylene group, alinear alkyl group having 1 to 5 carbon atoms is preferable.

The linear or branched aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include a fluorine atom, afluorinated alkyl group having 1 to 5 carbon atoms, which is substitutedwith a fluorine atom, and a carbonyl group.

Aliphatic Hydrocarbon Group Containing Ring in Structure Thereof

Examples of the aliphatic hydrocarbon group containing a ring in astructure thereof include an optionally substituted cyclic aliphatichydrocarbon group containing a hetero atom in a ring structure thereof(a group in which two hydrogen atoms are eliminated from an aliphatichydrocarbon ring), a group in which the cyclic aliphatic hydrocarbongroup is bonded to the terminal of a linear or branched aliphatichydrocarbon group, and a group in which the cyclic aliphatic hydrocarbongroup intervenes on the way of a linear or branched aliphatichydrocarbon group. Examples of the linear or branched aliphatichydrocarbon group include the same groups as those described above.

The cyclic aliphatic hydrocarbon group has preferably 3 to 20 carbonatoms, and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be either a polycyclic groupor a monocyclic group. The monocyclic alicyclic hydrocarbon group ispreferably a group in which two hydrogen atoms are eliminated from amonocycloalkane. The monocycloalkane is preferably one having 3 to 6carbon atoms. Specifically, examples thereof include cyclopentane andcyclohexane. The polycyclic alicyclic hydrocarbon group is preferably agroup in which two hydrogen atoms are eliminated from a polycycloalkane.The polycycloalkane is preferably one having 7 to 12 carbon atoms.Specifically, examples thereof include adamantane, norbornane,isobornane, tricyclodecane, and tetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup, and a carbonyl group.

The alkyl group as the substituent is preferably an alkyl group having 1to 5 carbon atoms, and most preferably a methyl group, an ethyl group, apropyl group, an n-butyl group, or a tert-butyl group.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group,an n-propoxy group, an isopropoxy group, an n-butoxy group, or atert-butoxy group, and most preferably a methoxy group or an ethoxygroup.

Examples of the halogen atom as the substituent include a fluorine atom,a chlorine atom, a bromine atom, and an iodine atom, with a fluorineatom being preferable.

Examples of the halogenated alkyl group as the substituent include agroup in which some or all the hydrogen atoms of the above-describedalkyl group are substituted with the above-described halogen atom.

In the cyclic aliphatic hydrocarbon group, some of the carbon atomsconstituting the ring structure thereof may be substituted with asubstituent containing a hetero atom. The substituent containing ahetero atom is preferably —O—, —C(═O)—O—, —S—, —S(═O)₂—, or —S(═C)₂—O—.

Aromatic Hydrocarbon Group in Ya⁰¹

The aromatic hydrocarbon group is a hydrocarbon group having at leastone aromatic ring.

This aromatic ring is not particularly limited so long as it is a cyclicconjugated system having (4n+2) π electrons, and it may be eithermonocyclic or polycyclic. The number of carbon atoms of the aromaticring is preferably 5 to 30, more preferably 5 to 20, still morepreferably 6 to 15, and especially preferably 6 to 12. However, thenumber of carbon atoms does not include the number of carbon atoms inthe substituent. Specifically, examples of the aromatic ring include anaromatic hydrocarbon ring such as benzene, naphthalene, anthracene, andphenanthrene; and an aromatic heterocyclic ring in which some of thecarbon atoms constituting the above-described aromatic hydrocarbon ringare substituted with a hetero atom. Examples of the hetero atom in thearomatic heterocyclic ring include an oxygen atom, a sulfur atom, and anitrogen atom. Specifically, examples of the aromatic heterocyclic ringinclude a pyridine ring and a thiophene ring.

Specifically, examples of the aromatic hydrocarbon group include a groupin which two hydrogen atoms are eliminated from the above-describedaromatic hydrocarbon ring or aromatic heterocyclic ring (an arylenegroup or a heteroarylene group); a group in which two hydrogen atoms areeliminated from an aromatic compound containing two or more aromaticrings (for example, biphenyl or fluorene); and a group in which onehydrogen atom of a group in which one hydrogen atom is eliminated fromthe above-described aromatic hydrocarbon ring or aromatic heterocyclicring (an aryl group or a heteroaryl group) is substituted with analkylene group (for example, a group in which one hydrogen atom isfurther eliminated from an aryl group in an arylalkyl group such as abenzyl group, a phenethyl group, a 1-naphthylmethyl group, a2-naphthylmethyl group, a 1-naphthylethyl group, and a 2-naphthylethylgroup). The number of carbon atoms of the alkylene group bonded to theabove-described aryl group or heteroaryl group is preferably 1 to 4,more preferably 1 to 2, and especially preferably 1.

In the above-described aromatic hydrocarbon group, the hydrogen atom(s)which the aromatic hydrocarbon group has may be substituted with asubstituent. For example, the hydrogen atom(s) bonded to the aromaticring in the aromatic hydrocarbon group may be substituted with asubstituent. Examples of the substituent include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, and a hydroxylgroup.

The alkyl group as the substituent is preferably an alkyl group having 1to 5 carbon atoms. The alkyl group is most preferably a methyl group, anethyl group, a propyl group, an n-butyl group, or a tert-butyl group.

Examples of the alkoxy group, the halogen atom, and the halogenatedalkyl group as the substituent include those exemplified above for thesubstituent with which the hydrogen atom(s) which the cyclic aliphatichydrocarbon group has is substituted.

Hetero Atom-Containing Divalent Linking Group:

When Ya⁰¹ represents a hetero atom-containing divalent linking group,preferred examples of the linking group include —O—, —C(═O)—O—, —C(═O)—,—O—C(═O)—O—, —C(═O)—NH—, —NH—, —NH—C(═NH)— (H may be substituted with asubstituent such as an alkyl group and an acyl group), —S—, —S(═O)₂—,—S(═O)₂—O—, and a group represented by a general formula: —Y²¹—O—Y²²—,—Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—, —[Y²¹C(═O)—O]_(m″)—Y²²—,—Y²¹—O—C(═O)—Y²²—, or —Y²¹—S(═O)₂—O—Y²²—. In the formulae, each of Y²¹and Y²² independently represents an optionally substituted divalenthydrocarbon group, O represents an oxygen atom, and m″ represents aninteger of 0 to 3.

When the hetero atom-containing divalent linking group is —C(═O)—NH—,—C(═O)—NH—C(═O)—, —NH—, or —NH—C(═NH)—, H may be substituted with asubstituent such as an alkyl group and an acyl group. The number ofcarbon atoms of the substituent (such as an alkyl group and an acylgroup) is preferably 1 to 10, more preferably 1 to 8, and especiallypreferably 1 to 5.

In the general formula: —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—,—C(═O)—O—Y²¹—, —[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²—, or—Y²¹—S(═O)₂—O—Y²²—, each of Y²¹ and Y²² independently represents anoptionally substituted divalent hydrocarbon group. Examples of thedivalent hydrocarbon group include the same divalent hydrocarbon groupsas those exemplified above for the divalent linking group (optionallysubstituted divalent hydrocarbon group).

Y²¹ is preferably a linear aliphatic hydrocarbon group, more preferablya linear alkylene group, still more preferably a linear alkylene grouphaving 1 to 5 carbon atoms, and especially preferably a methylene groupor an ethylene group.

Y²² is preferably a linear or branched aliphatic hydrocarbon group, andmore preferably a methylene group, an ethylene group, or analkylmethylene group. The alkyl group in the alkylmethylene group ispreferably a linear alkyl group having 1 to 5 carbon atoms, morepreferably a linear alkyl group having 1 to 3 carbon atoms, and mostpreferably a methyl group.

In the group represented by the formula: —[Y²¹—C(═O)—O]_(m″)—Y²²—, m″represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and especially preferably 1. Namely, the grouprepresented by the formula: —[Y²¹—C(═O)—O]_(m″)—Y²²— is especiallypreferably a group represented by the formula: —Y²¹—C(═O)—O—Y²²—. Aboveall, a group represented by the formula: —(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)—is preferable. In the foregoing formula, a′ represents an integer of 1to 10, preferably an integer of 1 to 8, more preferably an integer of 1to 5, still more preferably 1 or 2, and most preferably 1. b′ representsan integer of 1 to 10, preferably 1 to 8, more preferably 1 to 5, stillmore preferably 1 or 2, and most preferably 1.

Ya⁰¹ is preferably a single bond, an ester bond [—C(═O)—O—], an etherbond (—O—), a linear or branched alkylene group, or a combinationthereof. Of these, Ya⁰¹ is more preferably a single bond.

In the formula (a0-1), X⁰¹ is a sulfur atom or an oxygen atom, and anoxygen atom is preferable.

In the formula (a0-1), Ra⁰¹ is an optionally substituted cyclic group,an optionally substituted chain alkyl group, or an optionallysubstituted chain alkenyl group.

Optionally Substituted Cyclic Group:

The cyclic group is preferably a cyclic hydrocarbon group. The cyclichydrocarbon group may be an aromatic hydrocarbon group or a cyclicaliphatic hydrocarbon group. The aliphatic hydrocarbon group means ahydrocarbon group having no aromaticity. In addition, the aliphatichydrocarbon group may be either saturated or unsaturated, and ingeneral, it is preferably saturated.

The aromatic hydrocarbon group in Ra⁰¹ is a hydrocarbon group having atleast one aromatic ring.

This aromatic ring is not particularly limited so long as it is a cyclicconjugated system having (4n+2) π electrons, and it may be eithermonocyclic or polycyclic. The number of carbon atoms of the aromaticring is preferably 5 to 30, more preferably 5 to 20, still morepreferably 6 to 15, and especially preferably 6 to 12. However, thenumber of carbon atoms does not include the number of carbon atoms inthe substituent. Specifically, examples of the aromatic ring include anaromatic hydrocarbon ring such as benzene, naphthalene, anthracene, andphenanthrene; and an aromatic heterocyclic ring in which some of thecarbon atoms constituting the above-described aromatic hydrocarbon ringare substituted with a hetero atom. Examples of the hetero atom in thearomatic heterocyclic ring include an oxygen atom, a sulfur atom, and anitrogen atom. Specifically, examples of the aromatic heterocyclic ringinclude a pyridine ring and a thiophene ring.

Specifically, examples of the aromatic hydrocarbon group in Ra⁰¹ includea group in which one hydrogen atom is eliminated from theabove-described aromatic hydrocarbon ring or aromatic heterocyclic ring(an aryl group or a heteroaryl group); a group in which one hydrogenatom is eliminated from an aromatic compound containing two or morearomatic rings (for example, biphenyl or fluorene); and a group in whichone hydrogen atom of the above-described aromatic hydrocarbon ring oraromatic heterocyclic ring is substituted with an alkylene group (forexample, an arylalkyl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, and a 2-naphthylethyl group). The number of carbon atoms of thealkylene group bonded to the above-described aromatic hydrocarbon ringor aromatic heterocyclic ring is preferably 1 to 4, more preferably 1 to2, and especially preferably 1.

Examples of the cyclic aliphatic hydrocarbon group in Ra⁰¹ include analiphatic hydrocarbon group containing a ring in a structure thereof.

Examples of the aliphatic hydrocarbon group containing a ring in astructure thereof include an alicyclic hydrocarbon group (a group inwhich one hydrogen atom is eliminated from an aliphatic hydrocarbonring), a group in which an alicyclic hydrocarbon group is bonded to theterminal of a linear or branched aliphatic hydrocarbon group, and agroup in which an alicyclic hydrocarbon group intervenes on the way of alinear or branched aliphatic hydrocarbon group.

The number of carbon atoms of the above-described alicyclic hydrocarbongroup is preferably 3 to 20, and more preferably 3 to 12.

The above-described alicyclic hydrocarbon group may be either apolycyclic group or a monocyclic group. The monocyclic alicyclichydrocarbon group is preferably a group in which one or more hydrogenatoms are eliminated from a monocycloalkane. The monocycloalkane ispreferably one having 3 to 6 carbon atoms, and specifically, examplesthereof include cyclopentane and cyclohexane. The polycyclic alicyclichydrocarbon group is preferably a group in which one or more hydrogenatoms are eliminated from a polycycloalkane. The polycycloalkane ispreferably one having 7 to 12 carbon atoms, and specifically, examplesthereof include adamantane, norbornane, isobornane, tricyclodecane, andtetracyclododecane.

Above all, the alicyclic hydrocarbon group in Ra⁰¹ is preferably apolycyclic group, more preferably a group in which one hydrogen atom iseliminated from a polycycloalkane, especially preferably an adamantylgroup or a norbornyl group, and most preferably an adamantyl group.

The number of carbon atoms of the linear or branched aliphatichydrocarbon group which may be bonded to an alicyclic hydrocarbon groupis preferably 1 to 10, more preferably 1 to 6, still more preferably 1to 4, and most preferably 1 to 3.

The linear aliphatic hydrocarbon group is preferably a linear alkylenegroup. Specifically, examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—], and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group is preferably a branchedalkylene group. Specifically, examples thereof include an alkylalkylenegroup such as an alkylmethylene group, for example, —CH(CH₃)—,—CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and—C(CH₂CH₃)₂—; an alkylethylene group, for example, —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—;an alkyltrimethylene group, for example, —CH(CH₃)CH₂CH₂— and—CH₂CH(CH₃)CH₂—; and an alkyltetramethylene group, for example,—CH(CH₃)CH₂CH₂CH₂— and —CH₂CH(CH₃)CH₂CH₂—. The alkyl group in thealkylalkylene group is preferably a linear alkyl group having 1 to 5carbon atoms.

In addition, the cyclic hydrocarbon group in Ra⁰¹ may contain a heteroatom as in a heterocyclic ring or the like. Specifically, examplesthereof include lactone-containing cyclic groups represented by generalformulae (a2-r-1) to (a2-r-7) to be described later, respectively, and—SO₂-containing cyclic groups represented by general formulae (a5-r-1)to (a5-r-4) to be described later, respectively, and besides,heterocyclic groups which will be exemplified below. Of these,lactone-containing cyclic groups represented by the general formulae(a2-r-1) to (a2-r-7), respectively, and —SO₂-containing cyclic groupsrepresented by the general formulae (a5-r-1) to (a5-r-4), respectivelyare especially preferable. In the formulae, * represents a bond (and hasthe same usage below).

Examples of the substituent which the cyclic group represented by Ra⁰¹may have include an alkyl group, an alkoxy group, a halogen atom, ahalogenated alkyl group, a hydroxyl group, a carbonyl group (—C(═O)—),an ether bond (—O—), an ester bond (—C(═O)—O—), and a nitro group.

The alkyl group as the substituent is preferably an alkyl group having 1to 5 carbon atoms, and most preferably a methyl group, an ethyl group, apropyl group, an n-butyl group, or a tert-butyl group.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group,an n-propoxy group, an isopropoxy group, an n-butoxy group, or atert-butoxy group, and most preferably a methoxy group or an ethoxygroup.

Examples of the halogen atom as the substituent include a fluorine atom,a chlorine atom, a bromine atom, and an iodine atom, with a fluorineatom being preferable.

Examples of the halogenated alkyl group as the substituent include agroup in which some or all the hydrogen atoms of an alkyl group having 1to 5 carbon atoms, for example, a methyl group, an ethyl group, a propylgroup, an n-butyl group, or a tert-butyl group, are substituted with theabove-described halogen atom.

The carbonyl group (—C(═O)—), the ether bond (—O—), and the ester bond(—C(═O)—O—) as the substituent are groups with which a methylene group(—CH₂—) constituting the cyclic group is substituted.

Optionally Substituted Chain Alkyl Group:

The chain alkyl group in Ra⁰¹ may be either linear or branched.

The number of carbon atoms of the linear alkyl group is preferably 1 to20, more preferably 1 to 15, still more preferably 1 to 10, andespecially preferably 1 to 5. Specifically, examples thereof include amethyl group, an ethyl group, a propyl group, a butyl group, a pentylgroup, a hexyl group, a heptyl group, an octyl group, a nonyl group, adecanyl group, an undecyl group, a dodecyl group, a tridecyl group, anisotridecyl group, a tetradecyl group, a pentadecyl group, a hexadecylgroup, an isohexadecyl group, a heptadecyl group, an octadecyl group, anonadecyl group, an eicosyl group, a heneicosyl group, and a docosylgroup.

The number of carbon atoms of the branched alkyl group is preferably 3to 20, more preferably 3 to 15, and still more preferably 3 to 10.Specifically, examples thereof include a 1-methylethyl group, a1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a3-methylpentyl group, and a 4-methylpentyl group.

Optionally Substituted Chain Alkenyl Group

The chain alkenyl group in Ra⁰¹ may be either linear or branched. Thenumber of carbon atoms of the chain alkenyl group is preferably 2 to 10,more preferably 2 to 5, still more preferably 2 to 4, and especiallypreferably 3. Examples of the linear alkenyl group include a vinylgroup, a propenyl group (allyl group), and a butynyl group. Examples ofthe branched alkenyl group include a 1-methylvinyl group, a2-methylvinyl group, a 1-methylpropenyl group, and a 2-methylpropenylgroup.

Above all, the chain alkenyl group is more preferably a vinyl group or apropenyl group, and especially preferably a vinyl group.

Examples of the substituent which the chain alkyl group or chain alkenylgroup in Ra⁰¹ may have include an alkoxy group, a halogen atom, ahalogenated alkyl group, a hydroxyl group, a carbonyl group (—C(═O)—),an ether bond (—O—), an ester bond (—C(═O)—O—), a nitro group, an aminogroup, and the cyclic groups in the above-described Ra⁰¹.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group,an n-propoxy group, an isopropoxy group, an n-butoxy group, or atert-butoxy group, and most preferably a methoxy group or an ethoxygroup.

Examples of the halogen atom as the substituent include a fluorine atom,a chlorine atom, a bromine atom, and an iodine atom, with a fluorineatom being preferable.

Examples of the halogenated alkyl group as the substituent include agroup in which some or all the hydrogen atoms of an alkyl group having 1to 5 carbon atoms, for example, a methyl group, an ethyl group, a propylgroup, an n-butyl group, or a tert-butyl group, are substituted with theabove-described halogen atom.

The carbonyl group (—C(═O)—), the ether bond (—O—), and the ester bond(—C(═O)—O—) as the substituent are groups with which a methylene group(—CH₂—) constituting the chain alkyl group or chain alkenyl group issubstituted.

Of the foregoing, Ra⁰¹ is preferably an optionally substituted cyclicgroup, and more preferably an optionally substituted cyclic hydrocarbongroup in view of the fact that sensitivity further increases in theformation of a resist pattern. Above all, Ra⁰¹ is especially preferablyan aromatic hydrocarbon group or an aliphatic hydrocarbon groupcontaining a polycyclic group in a structure thereof (a carbon atom or ahydrogen atom of the aromatic hydrocarbon group or the aliphatichydrocarbon group may be substituted with a substituent), and mostpreferably an aliphatic hydrocarbon group containing a polycyclic groupin a structure thereof (a carbon atom or a hydrogen atom of thealiphatic hydrocarbon group may be substituted with a substituent),since good sensitivity is maintained, roughness is further decreased,and the thickness (pattern height) of a resist film hardly varies beforeand after development.

Preferred examples of the constituent unit (a0) include constituentunits represented by the following general formula (a0-1-1), (a0-1-2),or (a0-1-3) in view of the fact that sensitivity, resolution, andlithography properties are further enhanced.

In the formula, R represents a hydrogen atom, an alkyl group having 1 to5 carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms;X⁰¹ represents a sulfur atom or an oxygen atom; Ra⁰¹¹ represents anaromatic hydrocarbon group (a carbon atom or a hydrogen atom of thearomatic hydrocarbon group may be substituted with a substituent); Ra⁰¹²represents an aliphatic hydrocarbon group containing a polycyclic group(a carbon atom or a hydrogen atom of the aliphatic hydrocarbon group maybe substituted with a substituent); Ra⁰¹³ represents an aliphatichydrocarbon group other than the group represented by Ra⁰¹² (a carbonatom or a hydrogen atom of the aliphatic hydrocarbon group may besubstituted with a substituent); each of d1, d2, and d3 represents 0 or1; and each of e1, e2, and e3 represents an integer of 1 to 5.

In the formula (a0-1-1), (a0-1-2), or (a0-1-3), R is the same as R inthe formula (a0-1).

X⁰¹ is a sulfur atom or an oxygen atom, and is preferably an oxygenatom.

In the formula (a0-1-1), the aromatic hydrocarbon group in Ra⁰¹¹ is thesame as the aromatic hydrocarbon group in Ra⁰¹ in the formula (a0-1).Ra⁰¹¹ is preferably a group in which one hydrogen atom is eliminatedfrom an aromatic ring (aromatic hydrocarbon ring), and especiallypreferably a phenyl group or a naphthyl group. The substituent withwhich the aromatic hydrocarbon group in Ra⁰¹¹ is substituted is the sameas that in the description of the substituent which the above-describedcyclic group represented by Ra⁰¹ may have.

The hydrogen atom of the aromatic hydrocarbon group in Ra⁰¹¹ ispreferably substituted with a substituent, and is more preferablysubstituted with a halogen atom. The halogen atom is preferably afluorine atom or a bromine atom.

In the formula (a0-1-2), the aliphatic hydrocarbon group containing apolycyclic group in Ra⁰¹² is the same as the aliphatic hydrocarbon groupcontaining a polycyclic group in the description of the cyclic aliphatichydrocarbon group in Ra⁰¹ in the formula (a0-1). Ra⁰¹² is preferably analicyclic hydrocarbon group which is a polycyclic group or aheterocyclic group which is a polycyclic group, and more preferably agroup in which one hydrogen atom is eliminated from a polycycloalkane ora lactone-containing cyclic group.

The substituent with which the aliphatic hydrocarbon group containing apolycyclic group in Ra⁰¹² is substituted is the same as that in thedescription of the substituent which the above-described cyclic group inRa⁰¹ may have.

In the formula (a0-1-3), Ra⁰¹³ is the same as the group other than thealiphatic hydrocarbon group containing a polycyclic group (an aliphatichydrocarbon group containing a monocyclic group), the optionallysubstituted chain alkyl group, and the optionally substituted chainalkenyl group in the description of the cyclic aliphatic hydrocarbongroup in Ra⁰¹ in the formula (a0-1).

Specific examples of the constituent unit (a0) are given below. In thefollowing formulae, R^(α) represents a hydrogen atom, a methyl group, ora trifluoromethyl group.

The constituent unit (a0) is preferably at least one kind selected fromthe group consisting of constituent units represented by the generalformulae (a0-1-1), (a0-1-2), and (a0-1-3), respectively. It is morepreferably at least one kind selected from the group consisting ofconstituent units represented by the general formulae (a0-1-1) and(a0-1-2), respectively, and especially preferably a constituent unitrepresented by the general formula (a0-1-2), since a roughnessdecreasing effect and an effect of securing the thickness (patternheight) of a resist film after development are more easily obtained.

Specifically, constituent units represented by the formulae (a0-1-212),(a0-1-214), (a0-1-219), (a0-1-220), and (a0-1-221), respectively, arepreferable. Of these, constituent units represented by the formulae(a0-1-212) and (a0-1-214), respectively, are especially preferable.

The constituent unit (a0) which the component (A1) has may be either onekind or two or more kinds.

A proportion of the constituent unit (a0) in the component (A1) ispreferably 35 mol % or less, more preferably 30 mol % or less, stillmore preferably 5 mol % to 30 mol %, and especially preferably 10 mol %to 30 mol % relative to a total sum of all of the constituent unitsconstituting the component (A1).

When the proportion of the constituent unit (a0) is not more than thepreferred upper limit value, high sensitivity is maintained and a resistpattern having a good shape with decreased roughness is easily obtained.On the other hand, when the proportion of the constituent unit (a0) isthe preferred lower limit value or more, sensitivity increases, andresolution and lithography properties are also enhanced.

Constituent Unit (a1-1)

The constituent unit (a1-1) is a constituent unit including a monocyclicgroup-containing acid decomposable group whose polarity increases by theaction of an acid.

The term “acid decomposable group” refers to a group having aciddecomposability, in which at least a part of the bond in the structureof the acid decomposable group may be cleaved by the action of an acid.

Examples of the acid decomposable group whose polarity increases by theaction of an acid include a group which is decomposed by the action ofan acid to form a polar group.

Examples of the polar group include a carboxy group, a hydroxyl group,an amino group, and a sulfo group (—SO₃H). Of these, a polar groupcontaining —OH in a structure thereof (hereinafter, sometimes referredto as “OH-containing polar group”) is preferable, a carboxy group or ahydroxyl group is more preferable, and a carboxy group is especiallypreferable.

More specifically, examples of the acid decomposable group include agroup in which the above-described polar group is protected by an aciddissociable group (for example, a group in which the hydrogen atom ofthe OH-containing polar group is protected by an acid dissociablegroup).

Here, the term “acid dissociable group” refers to either one or both ofthe following groups: (i) a group having such acid dissociationproperties that the bond between the acid dissociable group and the atomadjacent to the acid dissociable group may be cleaved by the action ofan acid, and (ii) a group in which after a part of the bond is cleavedby the action of an acid, a decarboxylation reaction is further caused,whereby the bond between the acid dissociable group and the atomadjacent to the acid dissociable group may be cleaved.

It is necessary that the acid dissociable group constituting the aciddecomposable group is a group with lower polarity than a polar groupformed upon dissociation of the acid dissociable group. According tothis, on the occasion of dissociation of the acid dissociable group bythe action of an acid, a polar group having higher polarity than theacid dissociable group is formed, whereby the polarity increases. As aresult, the polarity of the whole of the component (A1) increases. Whenthe polarity increases, the solubility in a developing solutionrelatively changes. In the case where the developing solution is analkali developing solution, the solubility increases, and in the casewhere the developing solution is an organic developing solution, thesolubility decreases.

Examples of the acid dissociable group include those which have been sofar proposed as an acid dissociable group of a base resin for achemically amplified resist.

Specific examples of those proposed as an acid dissociable group of abase resin for a chemically amplified resist include an “acetal typeacid dissociable group” a “tertiary alkyl ester type acid dissociablegroup”, and a “tertiary alkyloxycarbonyl acid dissociable group” to bedescribed as follows.

Acetal-Type Acid Dissociable Group:

Examples of the acid dissociable group which protects a carboxy group ora hydroxyl group among the above-described polar groups include an aciddissociable group represented by the following general formula (a1-r-1)(hereinafter, sometimes referred to as “acetal type acid dissociablegroup”).

In the formula, each of Ra′¹ and Ra′² represents a hydrogen atom or analkyl group; Ra′³ represents a hydrocarbon group; and Ra′³ may be bondedto either Ra′¹ or Ra′² to form a ring.

In the formula (a1-r-1), it is preferable that at least one of Ra′¹ andRa′² is a hydrogen atom, and it is more preferable that both of Ra′¹ andRa′² are a hydrogen atom.

In the case where Ra′¹ or Ra′² is an alkyl group, examples of the alkylgroup include the same alkyl groups as those exemplified as thesubstituent which may be bonded to the carbon atom at the α-position inthe description of the α-substituted acrylic ester, and an alkyl grouphaving 1 to 5 carbon atoms is preferable. Specifically, there ispreferably exemplified a linear or branched alkyl group. Morespecifically, examples thereof include a methyl group, an ethyl group, apropyl group, an isopropyl group, an n-butyl group, an isobutyl group, atert-butyl group, a pentyl group, an isopentyl group, and a neopentylgroup. A methyl group or an ethyl group is more preferable, and a methylgroup is especially preferable.

In the formula (a1-r-1), examples of the hydrocarbon group representedby Ra′³ include a linear or branched alkyl group and a cyclichydrocarbon group.

The number of carbon atoms of the linear alkyl group is preferably 1 to5, more preferably 1 to 4, and still more preferably 1 or 2.Specifically, examples thereof include a methyl group, an ethyl group,an n-propyl group, an n-butyl group, and an n-pentyl group. Of these, amethyl group, an ethyl group, or an n-butyl group is preferable, and amethyl group or an ethyl group is more preferable.

The number of carbon atoms of the branched alkyl group is preferably 3to 10, and more preferably 3 to 5. Specifically, examples thereofinclude an isopropyl group, an isobutyl group, a tert-butyl group, anisopentyl group, a neopentyl group, a 1,1-diethylpropyl group, and a2,2-dimethylbutyl group, with an isopropyl group being preferable.

In the case where Ra′³ is a cyclic hydrocarbon group, the hydrocarbongroup may be either aliphatic or aromatic, and it may be either apolycyclic group or a monocyclic group.

The monocyclic aliphatic hydrocarbon group is preferably a group inwhich one hydrogen atom is eliminated from a monocycloalkane. Themonocycloalkane is preferably one having 3 to 6 carbon atoms.Specifically, examples thereof include cyclopropane, cyclopentane andcyclohexane, and cyclopentane and cyclohexane are preferable.

The polycyclic aliphatic hydrocarbon group is preferably a group inwhich one hydrogen atom is eliminated from a polycycloalkane. Thepolycycloalkane is preferably one having 7 to 12 carbon atoms, andspecifically, examples thereof include adamantane, norbornane,isobornane, tricyclodecane, and tetracyclododecane.

In the case where the cyclic hydrocarbon group represented by Ra′³ is anaromatic hydrocarbon group, the aromatic hydrocarbon group is ahydrocarbon group having at least one aromatic ring.

This aromatic ring is not particularly limited so long as it is a cyclicconjugated system having (4n+2) π electrons, and it may be eithermonocyclic or polycyclic. The number of carbon atoms of the aromaticring is preferably 5 to 30, more preferably 5 to 20, still morepreferably 6 to 15, and especially preferably 6 to 12. Specifically,examples of the aromatic ring include an aromatic hydrocarbon ring suchas benzene, naphthalene, anthracene, and phenanthrene; and an aromaticheterocyclic ring in which some of the carbon atoms constituting theabove-described aromatic hydrocarbon ring are substituted with a heteroatom. Examples of the hetero atom in the aromatic heterocyclic ringinclude an oxygen atom, a sulfur atom, and a nitrogen atom.Specifically, examples of the aromatic heterocyclic ring include apyridine ring and a thiophene ring.

Specifically, examples of the aromatic hydrocarbon group in Ra′³ includea group in which one hydrogen atom is eliminated from theabove-described aromatic hydrocarbon ring or aromatic heterocyclic ring(an aryl group or a heteroaryl group); a group in which one hydrogenatom is eliminated from an aromatic compound containing two or morearomatic rings (for example, biphenyl or fluorene); and a group in whichone hydrogen atom of the above-described aromatic hydrocarbon ring oraromatic heterocyclic ring is substituted with an alkylene group (forexample, an arylalkyl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, and a 2-naphthylethyl group). The number of carbon atoms of thealkylene group bonded to the above-described aromatic hydrocarbon ringor aromatic heterocyclic ring is preferably 1 to 4, more preferably 1 to2, and especially preferably 1.

In the case where Ra′³ is bonded to either Ra′¹ or Ra′² to form a ring,the cyclic group is preferably a 4-membered to 7-membered ring, and morepreferably a 4-membered to 6-membered ring. Specific examples of thecyclic group include a tetrahydropyranyl group and a tetrahydrofuranylgroup.

Tertiary Alkyl Ester Type Acid Dissociable Group:

Examples of the acid dissociable group which protects a carboxy groupamong the above-described polar groups include an acid dissociable grouprepresented by the following general formula (a1-r-2). It is to be notedthat among the acid dissociable groups represented by the followingformula (a1-r-2), a group constituted of an alkyl group is hereinaftersometimes referred to as “tertiary alkyl ester type acid dissociablegroup” for the sake of convenience.

In the formula, each of Ra′⁴ to Ra′⁶ represents a hydrocarbon group, andRa′⁵ and Ra′⁶ may be bonded to each other to form a ring.

Examples of the hydrocarbon group represented by Ra′⁴ to Ra′⁶ includethe same hydrocarbon groups as those exemplified above for Ra′³.

Ra′⁴ is preferably an alkyl group having 1 to 5 carbon atoms. In thecase where Ra′⁵ and Ra′⁶ are bonded to each other to form a ring, agroup represented by the following general formula (a1-r-1) isexemplified. On the other hand, in the case where Ra′⁴ to Ra′⁶ are notbonded to each other and are each an independent hydrocarbon group, agroup represented by the following general formula (a1-r-2) isexemplified.

In the formulae, Ra′¹⁰ represents an alkyl group having 1 to 10 carbonatoms; Ra′¹¹ represents a group for forming an aliphatic cyclic grouptogether with the carbon atom to which Ra′¹⁰ is bonded; and each ofRa′¹² to Ra′¹⁴ independently represents a hydrocarbon group.

In the formula (a1-r2-1), the alkyl group having 1 to 10 carbon atomsrepresented by Ra′¹⁰ is preferably the group exemplified as the linearor branched alkyl group represented by Ra′³ in the formula (a1-r-1). Inthe formula (a1-r-1), as the aliphatic cyclic group which Ra′¹¹ formstogether with the carbon atom to which Ra′¹⁰ is bonded, the groupsexemplified as the aliphatic hydrocarbon group represented by Ra′³ inthe formula (a1-r-1), which is either a monocyclic group or a polycyclicgroup, are preferable.

In the formula (a1-r2-2), each of Ra′¹² and Ra′¹⁴ is preferablyindependently an alkyl group having 1 to 10 carbon atoms. The alkylgroup is more preferably the group exemplified as the linear or branchedalkyl group represented by Ra′³ in the formula (a1-r-1), still morepreferably a linear alkyl group having 1 to 5 carbon atoms, andespecially preferably a methyl group or an ethyl group.

In the formula (a1-r2-2), Ra′¹³ is preferably the linear or branchedalkyl group exemplified as the hydrocarbon group represented by Ra′³ inthe formula (a1-r-1), or an aliphatic hydrocarbon group which is eithera monocyclic group or a polycyclic group. Of these, Ra′¹³ is morepreferably the group exemplified as the aliphatic hydrocarbon grouprepresented by Ra′³, which is either a monocyclic group or a polycyclicgroup.

Specific examples of the group represented by the formula (a1-r2-1) aregiven below.

Specific examples of each of the groups represented by the formula(a1-r2-2) are given below.

Tertiary Alkyloxycarbonyl Acid Dissociable Group:

Examples of the acid dissociable group which protects a hydroxyl groupamong the above-described polar groups include an acid dissociable grouprepresented by the following general formula (a1-r-3) (hereinafter,sometimes referred to as “tertiary alkyloxycarbonyl acid dissociablegroup” for the sake of convenience).

In the formula, each of Ra′⁷ to Ra′⁹ represents an alkyl group.

In the formula (a1-r-3), each of Ra′⁷ to Ra′⁹ is preferably an alkylgroup having 1 to 5 carbon atoms, and more preferably an alkyl grouphaving 1 to 3 carbon atoms.

In addition, the total number of carbon atoms of the respective alkylgroups is preferably 3 to 7, more preferably 3 to 5, and most preferably3 to 4.

Examples of the acid dissociable group in the constituent unit (a1-1)include the acid dissociable groups having a monocyclic group among theabove-exemplified “acetal type acid dissociable group”, “tertiary alkylester type acid dissociable group”, and “tertiary alkyloxycarbonyl aciddissociable group”, and any of these can be used. Above all, thetertiary alkyl ester type acid dissociable group is preferable.

Examples of the constituent unit (a1-1) include a constituent unitderived from an acrylic ester in which the hydrogen atom bonded to thecarbon atom at the α-position may be substituted with a substituent, aconstituent unit derived from acrylamide, a constituent unit in which atleast some of the hydrogen atoms of the hydroxyl group of a constituentunit derived from hydroxystyrene or a hydroxystyrene derivative areprotected by a substituent containing a monocyclic group-containing aciddecomposable group, and a constituent unit in which at least some of thehydrogen atoms in —C(═O)—OH of a constituent unit derived fromvinylbenzoic acid or a vinylbenzoic acid derivative are protected by asubstituent containing a monocyclic group-containing acid decomposablegroup.

Of the foregoing, the constituent unit (a1-1) is preferably aconstituent unit derived from an acrylic ester in which the hydrogenatom bonded to the carbon atom at the α-position may be substituted witha substituent.

Preferred specific examples of the constituent unit (a1-1) include aconstituent unit represented by the following general formula (a1-1-1)or (a1-1-2).

In the formulae, R represents a hydrogen atom, an alkyl group having 1to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbonatoms; Va¹ represents a divalent hydrocarbon group which may have anether bond; n_(a1) is 0 to 2; Ra¹ represents an acid dissociable grouprepresented by the formula (a1-r-1) or (a1-r-2) and represents amonocyclic group-containing acid dissociable group; Wa¹ represents an(n_(a2)+1)-valent hydrocarbon group; n_(a2) is 1 to 3; and Ra²represents an acid dissociable group represented by the formula (a1-r-1)or (a1-r-3) and represents a monocyclic group-containing aciddissociable group.

In the formula (a1-1-1), the alkyl group having 1 to 5 carbon atomsrepresented by R is preferably a linear or branched alkyl group having 1to 5 carbon atoms. Specifically, examples thereof include a methylgroup, an ethyl group, a propyl group, an isopropyl group, an n-butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group, and a neopentyl group. The halogenated alkyl grouphaving 1 to 5 carbon atoms is a group in which some or all hydrogenatoms of the alkyl group having 1 to 5 carbon atoms are substituted witha halogen atom. Examples of the halogen atom include a fluorine atom, achlorine atom, a bromine atom, and an iodine atom, with a fluorine atombeing especially preferable.

R is preferably a hydrogen atom, an alkyl group having 1 to 5 carbonatoms, or a fluorinated alkyl group having 1 to 5 carbon atoms, and ismost preferably a hydrogen atom or a methyl group in terms of easinessin industrial availability.

The hydrocarbon group represented by Va¹ may be an aliphatic hydrocarbongroup or an aromatic hydrocarbon group. The aliphatic hydrocarbon groupmeans a hydrocarbon group having no aromaticity. The aliphatichydrocarbon group as a divalent hydrocarbon group in Va¹ may be eithersaturated or unsaturated, and in general, it is preferably saturated.

More specifically, examples of the aliphatic hydrocarbon group in Va¹include a linear or branched aliphatic hydrocarbon group, and analiphatic hydrocarbon group containing a ring in a structure thereof.

In addition, Va¹ may have an ether bond (—O—) between carbon atoms ofthe divalent hydrocarbon group. One or two or more ether bonds may bepresent in Va¹.

The number of carbon atoms of the linear or branched aliphatichydrocarbon group is preferably 1 to 10, more preferably 1 to 6, stillmore preferably 1 to 4, and most preferably 1 to 3.

The linear aliphatic hydrocarbon group is preferably a linear alkylenegroup. Specifically, examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—], and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group is preferably a branchedalkylene group. Specifically, examples thereof include an alkylalkylenegroup such as an alkylmethylene group, for example, —CH(CH₃)—,—CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and—C(CH₂CH₃)₂—; an alkylethylene group, for example, —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—;an alkyltrimethylene group, for example, —CH(CH₃)CH₂CH₂— and—CH₂CH(CH₃)CH₂—; and an alkyltetramethylene group, for example,—CH(CH₃)CH₂CH₂CH₂— and —CH₂CH(CH₃)CH₂CH₂—. The alkyl group in thealkylalkylene group is preferably a linear alkyl group having 1 to 5carbon atoms.

Examples of the aliphatic hydrocarbon group containing a ring in astructure thereof include an alicyclic hydrocarbon group (a group inwhich two hydrogen atoms are eliminated from an aliphatic hydrocarbonring), a group in which an alicyclic hydrocarbon group is bonded to theterminal of a linear or branched aliphatic hydrocarbon group, and agroup in which an alicyclic hydrocarbon group intervenes on the way of alinear or branched aliphatic hydrocarbon group. Examples of the linearor branched aliphatic hydrocarbon group include the same groups as thosedescribed above.

The alicyclic hydrocarbon group has preferably 3 to 20 carbon atoms, andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either a polycyclic group or amonocyclic group. The monocyclic alicyclic hydrocarbon group ispreferably a group in which two hydrogen atoms are eliminated from amonocycloalkane. The monocycloalkane is preferably one having 3 to 6carbon atoms. Specifically, examples thereof include cyclopentane andcyclohexane.

The polycyclic alicyclic hydrocarbon group is preferably a group inwhich two hydrogen atoms are eliminated from a polycycloalkane. Thepolycycloalkane is preferably one having 7 to 12 carbon atoms.Specifically, examples thereof include adamantane, norbornane,isobornane, tricyclodecane, and tetracyclododecane.

The aromatic hydrocarbon group in Va¹ is a hydrocarbon group having atleast one aromatic ring. This aromatic ring is not particularly limitedso long as it is a cyclic conjugated system having (4n+2) π electrons,and it may be either monocyclic or polycyclic. The number of carbonatoms of the aromatic ring is preferably 5 to 30, more preferably 5 to20, still more preferably 6 to 15, and especially preferably 6 to 12.Specifically, examples of the aromatic ring include an aromatichydrocarbon ring such as benzene, naphthalene, anthracene, andphenanthrene; and an aromatic heterocyclic ring in which some of thecarbon atoms constituting the above-described aromatic hydrocarbon ringare substituted with a hetero atom. Examples of the hetero atom in thearomatic heterocyclic ring include an oxygen atom, a sulfur atom, and anitrogen atom. Specifically, examples of the aromatic heterocyclic ringinclude a pyridine ring and a thiophene ring.

Specifically, examples of the aromatic hydrocarbon group include a groupin which two hydrogen atoms are eliminated from the above-describedaromatic hydrocarbon ring or aromatic heterocyclic ring (an arylenegroup or a heteroarylene group); a group in which two hydrogen atoms areeliminated from an aromatic compound containing two or more aromaticrings (for example, biphenyl or fluorene); and a group in which onehydrogen atom of a group in which one hydrogen atom is eliminated fromthe above-described aromatic hydrocarbon ring or aromatic heterocyclicring (an aryl group or a heteroaryl group) is substituted with analkylene group (for example, a group in which one hydrogen atom isfurther eliminated from an aryl group in an arylalkyl group such as abenzyl group, a phenethyl group, a 1-naphthylmethyl group, a2-naphthylmethyl group, a 1-naphthylethyl group, and a 2-naphthylethylgroup). The number of carbon atoms of the alkylene group bonded to theabove-described aryl group or heteroaryl group is preferably 1 to 4,more preferably 1 to 2, and especially preferably 1.

In the formula (a1-1-2), the (n_(a2)+1)-valent hydrocarbon group in Wa¹may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group.The aliphatic hydrocarbon group means a hydrocarbon group having noaromaticity. The aliphatic hydrocarbon group may be either saturated orunsaturated, and in general, it is preferably saturated. Examples of thealiphatic hydrocarbon group include a linear or branched aliphatichydrocarbon group, an aliphatic hydrocarbon group containing a ring in astructure thereof, and a group in which a linear or branched aliphatichydrocarbon group and an aliphatic hydrocarbon group containing a ringin a structure thereof are combined.

The valence of (n_(a2)+1) is preferably divalent to tetravalent, andmore preferably divalent or trivalent.

Specific examples of the constituent unit (a1-1) are given below. Ineach of the following formulae, R^(α) represents a hydrogen atom, amethyl group, or a trifluoromethyl group.

The constituent unit (a1-1) which the component (A1) has may be eitherone kind or two or more kinds.

A proportion of the constituent unit (a1-1) in the component (A1) ispreferably 1 mol % to 50 mol %, more preferably 5 mol % to 45 mol %, andstill more preferably 5 mol % to 40 mol % relative to a total sum of allof the constituent units constituting the component (A1).

When the proportion of the constituent unit (a1-1) is the preferredlower limit value or more, lithography properties such as an improvementof roughness are enhanced. On the other hand, when the proportion of theconstituent unit (a1-1) is not more than the preferred upper limitvalue, the thickness (pattern height) of a resist film hardly variesbefore and after development.

Other Constituent Units

The component (A1) may further have, in addition to the constituent unit(a0) and the constituent unit (a1-1), other constituent units which donot fall under the definitions of the constituent unit (a0) and theconstituent unit (a1-1).

The foregoing constituent units are not particularly limited so long asthey are a constituent unit which is not classified into theabove-described constituent units. A large number of constituent unitswhich have been conventionally known to be used for resins for resistsuch as those for ArF excimer lasers and KrF excimer lasers (preferablythose for ArF excimer lasers) can be used. Examples thereof includeconstituent units (a1-2) and (a2) to (a4) as described below andconstituent units which generate an acid upon exposure.

Constituent Unit (a1-2):

The constituent unit (a1-2) is a constituent unit including an aciddecomposable group whose polarity increases by the action of an acid,exclusive of the constituent unit (a1-1).

Examples of the acid dissociable group in the constituent unit (a1-2)include groups other than the acid dissociable groups having amonocyclic group among the above-exemplified “acetal type aciddissociable group”, “tertiary alkyl ester type acid dissociable group”,and “tertiary alkyloxycarbonyl acid dissociable group”. Above all, thetertiary alkyl ester type acid dissociable group is preferable.

Examples of the constituent unit (a1-2) include a constituent unitderived from an acrylic ester in which the hydrogen atom bonded to thecarbon atom at the α-position may be substituted with a substituent, aconstituent unit derived from acrylamide, a constituent unit in which atleast some of the hydrogen atoms of the hydroxyl group of a constituentunit derived from hydroxystyrene or a hydroxystyrene derivative areprotected by a substituent containing an acid decomposable group(exclusive of a monocyclic group-containing acid decomposable group),and a constituent unit in which at least some of the hydrogen atoms in—C(═O)—OH of a constituent unit derived from vinylbenzoic acid or avinylbenzoic acid derivative are protected by a substituent containingan acid decomposable group (exclusive of a monocyclic group-containingacid decomposable group).

Of the foregoing, the constituent unit (a1-2) is preferably aconstituent unit derived from an acrylic ester in which the hydrogenatom bonded to the carbon atom at the α-position may be substituted witha substituent.

Preferred specific examples of the constituent unit (a1-2) include aconstituent unit in which Ra¹ is an acid dissociable group (exclusive ofa monocyclic group-containing acid dissociable group) represented by theformula (a1-r-1) or (a1-r-2) in the constituent unit represented by thegeneral formula (a1-1-1), and a constituent unit in which Ra² is an aciddissociable group (exclusive of a monocyclic group-containing aciddissociable group) represented by the formula (a1-r-1) or (a1-r-3) inthe constituent unit represented by the general formula (a1-1-2).

Specific examples of the constituent unit (a1-2) are given below. Ineach of the following formulae, R^(α) represents a hydrogen atom, amethyl group, or a trifluoromethyl group.

The constituent unit (a1-2) which the component (A1) has may be eitherone kind or two or more kinds.

When the component (A1) has the constituent unit (a1-2), a proportion ofthe constituent unit (a1-2) in the component (A1) is preferably 1 mol %to 50 mol %, more preferably 5 mol % to 45 mol %, and still morepreferably 5 mol % to 40 mol % relative to a total sum of all of theconstituent units constituting the component (A1).

When the proportion of the constituent unit (a1-2) is the preferredlower limit value or more, etching resistance, depth of focus (DOF)characteristics, and the like are further improved. On the other hand,when the proportion of the constituent unit (a1-2) is not more than thepreferred upper limit value, sensitivity is easily maintained andlithography properties such as an improvement of roughness are alsofurther enhanced.

Constituent Unit (a2):

The constituent unit (a2) is a constituent unit containing alactone-containing cyclic group, an —SO₂-containing cyclic group, or acarbonate-containing cyclic group.

In the case of using the component (A1) for the formation of a resistfilm, the lactone-containing cyclic group, the —SO₂-containing cyclicgroup, or the carbonate-containing cyclic group of the constituent unit(a2) is effective for increasing the adhesion of the resist film to asubstrate.

The term “lactone-containing cyclic group” refers to a cyclic groupcontaining a ring (lactone ring) containing —O—C(═O)— in a ring skeletonthereof. When the lactone ring is counted as the first ring, alactone-containing cyclic group in which the only ring structure is thelactone ring is called a monocyclic group, whereas a lactone-containingcyclic group containing other ring structure is called a polycyclicgroup regardless of the structure of the other rings. Thelactone-containing cyclic group may be either a monocyclic group or apolycyclic group.

The lactone-containing cyclic group in the constituent unit (a2) is notparticularly limited, and any optional lactone-containing cyclic groupcan be used. Specifically, examples thereof include groups representedby the following general formulae (a2-r-1) to (a2-r-7), respectively.

In the formulae, each Ra′²¹ independently represents a hydrogen atom, analkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group,a hydroxyl group, —COOR″, —OC(═O)R″, a hydroxyalkyl group, or a cyanogroup; R″ represents a hydrogen atom, an alkyl group, alactone-containing cyclic group, a carbonate-containing cyclic group, ora SO₂-containing cyclic group; A″ represents an alkylene group having 1to 5 carbon atoms, which may contain an oxygen atom (—O—) or a sulfuratom (—S—), an oxygen atom, or a sulfur atom; n′ represents an integerof 0 to 2; and m′ represents 0 or 1.

In the general formulae (a2-r-1) to (a2-r-7), the alkyl group in Ra′²¹is preferably an alkyl group having 1 to 6 carbon atoms. The alkyl groupis preferably linear or branched. Specifically, examples thereof includea methyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group, a neopentyl group, and a hexyl group. Of these, amethyl group or an ethyl group is preferable, with a methyl group beingespecially preferable.

The alkoxy group in Ra′²¹ is preferably an alkoxy group having 1 to 6carbon atoms. The alkoxy group is preferably linear or branched.Specifically, examples thereof include a group in which the alkyl groupexemplified above as the alkyl group in Ra′²¹ and an oxygen atom (—O—)are connected to each other.

Examples of the halogen atom in Ra′²¹ include a fluorine atom, achlorine atom, a bromine atom, and an iodine atom, with a fluorine atombeing preferable.

Examples of the halogenated alkyl group in Ra′²¹ include a group inwhich some or all hydrogen atoms of the alkyl group in Ra′²¹ aresubstituted with a halogen atom. The halogenated alkyl group ispreferably a fluorinated alkyl group, and especially preferably aperfluoroalkyl group.

In —COOR″ and —OC(═O)R″ in Ra′²¹, each R″ is a hydrogen atom, an alkylgroup, a lactone-containing cyclic group, a carbonate-containing cyclicgroup, or a —SO₂-containing cyclic group.

The alkyl group in R″ may be linear, branched, or cyclic, and the numberof carbon atoms thereof is preferably 1 to 15.

In the case where R″ is a linear or branched alkyl group, the number ofcarbon atoms thereof is preferably 1 to 10, and more preferably 1 to 5.Above all, R″ is especially preferably a methyl group or an ethyl group.

In the case where R″ is a cyclic alkyl group, the number of carbon atomsthereof is preferably 3 to 15, more preferably 4 to 12, and mostpreferably 5 to 10. Specifically, examples thereof include a group inwhich one or more hydrogen atoms are eliminated from a monocycloalkane,which may or may not be substituted with a fluorine atom or afluorinated alkyl group; and a group in which one or more hydrogen atomsare eliminated from a polycycloalkane such as a bicycloalkane, atricycloalkane, and a tetracycloalkane. More specifically, examplesthereof include a group in which one or more hydrogen atoms areeliminated from a monocycloalkane such as cyclopentane and cyclohexane;and a group in which one or more hydrogen atoms are eliminated from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane, and tetracyclododecane.

Examples of the lactone-containing cyclic group in R″ include the samegroups as those represented by the general formulae (a2-r-1) to(a2-r-7), respectively.

The carbonate-containing cyclic group in R″ is the same as acarbonate-containing cyclic group to be described later. Specifically,examples thereof include groups represented by general formulae(ax3-r-1) to (ax3-r-3), respectively.

The —SO₂-containing cyclic group in R″ is the same as a —SO₂-containingcyclic group to be described later. Specifically, examples thereofinclude groups represented by general formulae (a5-r-1) to (a5-r-4),respectively.

The hydroxyalkyl group in Ra′²¹ is preferably one having 1 to 6 carbonatoms. Specifically, examples thereof include a group in which at leastone hydrogen atom of the alkyl group in Ra′²¹ is substituted with ahydroxyl group.

In the formulae (a2-r-2), (a2-r-3), and (a2-r-5), the alkylene grouphaving 1 to 5 carbon atoms in A″ is preferably a linear or branchedalkylene group, and examples thereof include a methylene group, anethylene group, an n-propylene group, and an isopropylene group. In thecase where the alkylene group contains an oxygen atom or a sulfur atom,specific examples thereof include a group in which —O— or —S— intervenesat the terminal or between the carbon atoms of the above-describedalkylene group. Examples thereof include —O—CH₂—, —CH₂—O—CH₂—, —S—CH₂—,and —CH₂—S—CH₂—. A″ is preferably an alkylene group having 1 to 5 carbonatoms or —O—, more preferably an alkylene group having 1 to 5 carbonatoms, and most preferably a methylene group.

Specific examples of each of the groups represented by the generalformulae (a2-r-1) to (a2-r-7) are given below.

The term “—SO₂-containing cyclic group” refers to a cyclic groupcontaining a ring containing —SO₂— in a ring skeleton thereof, andspecifically, it is a cyclic group in which the sulfur atom (S) in —SO₂—forms a part of the ring skeleton of the cyclic group. When the ringcontaining —SO₂— in the ring skeleton thereof is counted as the firstring, an —SO₂-containing cyclic group in which the only ring structureis the —SO₂-containing ring is called a monocyclic group, whereas an—SO₂-containing cyclic group containing other ring structure is called apolycyclic group regardless of the structure of the other rings. The—SO₂-containing cyclic group may be either a monocyclic group or apolycyclic group.

The —SO₂-containing cyclic group is especially preferably a cyclic groupcontaining —O—SO₂— in a ring skeleton thereof, namely a cyclic groupcontaining a sultone ring in which —O—S— in —O—SO₂— forms a part of thering skeleton.

More specifically, examples of the —SO₂-containing cyclic group includegroups represented by the following general formulae (a5-r-1) to(a5-r-4), respectively.

In the formulae, each Ra′⁵¹ independently represents a hydrogen atom, analkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group,a hydroxyl group, —COOR″, —OC(═O)R″, a hydroxyalkyl group, or a cyanogroup; R″ represents a hydrogen atom, an alkyl group, alactone-containing cyclic group, a carbonate-containing cyclic group, ora —SO₂-containing cyclic group; A″ represents an alkylene group having 1to 5 carbon atoms, which may contain an oxygen atom or a sulfur atom, anoxygen atom, or a sulfur atom; and n′ represents an integer of 0 to 2.

In the general formulae (a5-r-1) to (a5-r-4), A″ is the same as A″ inthe general formulae (a2-r-2), (a2-r-3), and (a2-r-5).

The alkyl group, the alkoxy group, the halogen atom, the halogenatedalkyl group, —COOR″, —OC(═O)R″, and the hydroxyalkyl group in Ra′⁵¹ arethe same as those exemplified in the description of Ra′²¹ in the generalformulae (a2-r-1) to (a2-r-7), respectively.

Specific examples of each of the groups represented by the generalformulae (a5-r-1) to (a5-r-4) are given below. In the followingformulae, “Ac” represents an acetyl group.

The term “carbonate-containing cyclic group” refers to a cyclic groupcontaining a ring containing —O—C(═O)—O— in a ring skeleton thereof(carbonate ring). When the carbonate ring is counted as the first ring,a carbonate-containing cyclic group in which the only ring structure isthe carbonate ring is called a monocyclic group, whereas acarbonate-containing cyclic group containing other ring structure iscalled a polycyclic group regardless of the structure of the otherrings. The carbonate-containing cyclic group may be either a monocyclicgroup or a polycyclic group.

The carbonate ring-containing cyclic group is not particularly limited,and any optional carbonate ring-containing cyclic group can be used.Specifically, examples thereof include groups represented by thefollowing general formulae (ax3-r-1) to (ax3-r-3), respectively.

In the formulae, each Ra′^(x31) independently represents a hydrogenatom, an alkyl group, an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, —COOR″, —OC(═O)R″, a hydroxyalkyl group,or a cyano group; R″ represents a hydrogen atom, an alkyl group, alactone-containing cyclic group, a carbonate-containing cyclic group, ora —SO₂-containing cyclic group; A″ represents an alkylene group having 1to 5 carbon atoms, which may contain an oxygen atom or a sulfur atom, anoxygen atom, or a sulfur atom; p′ represents an integer of 0 to 3; andq′ represents 0 or 1.

A″ in the general formulae (ax3-r-1) to (ax3-r-3) is the same as A″ inthe general formulae (a2-r-2), (a2-r-3), and (a2-r-5).

The alkyl group, the alkoxy group, the halogen atom, the halogenatedalkyl group, —COOR″, —OC(═O)R″, and the hydroxyalkyl group in Ra′^(x31)are the same as those exemplified in the description of Ra′²¹ in thegeneral formulae (a2-r-1) to (a2-r-7), respectively.

Specific examples of each of the groups represented by the generalformulae (ax3-r-1) to (ax3-r-3) are given below.

Of the foregoing, the constituent unit (a2) is preferably a constituentunit derived from an acrylic ester in which the hydrogen atom bonded tothe carbon atom at the α-position may be substituted with a substituent.

Such a constituent unit (a2) is preferably a constituent unitrepresented by the following general formula (a2-1).

In the formula, R represents a hydrogen atom, an alkyl group having 1 to5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms;Ya²¹ represents a single bond or a divalent linking group; La²¹represents —O—, —COO—, —CON(R′)—, —OCO—, —CONHCO—, or —CONHCS—; R′represents a hydrogen atom or a methyl group, provided that in the casewhere La²¹ is —O—, Ya²¹ is not —CO—; and Ra²¹ represents alactone-containing cyclic group, a carbonate-containing cyclic group, oran —SO₂-containing cyclic group.

In the formula (a2-1), R is the same as that described above.

Though the divalent linking group represented by Ya²¹ is notparticularly limited, preferred examples thereof include an optionallysubstituted divalent hydrocarbon group and a divalent linking groupcontaining a hetero atom.

Examples of the optionally substituted divalent hydrocarbon group inYa²¹ include the same optionally substituted divalent hydrocarbon groupas that in Ya⁰¹ in the formula (a0-1).

Examples of the divalent linking group containing a hetero atom in Ya²¹include the same divalent linking group containing a hetero atom as thatin Ya⁰¹ in the formula (a0-1).

Ya²¹ is preferably a single bond, an ester bond [—C(═O)—O—], an etherbond (—O—), a linear or branched alkylene group, or a combinationthereof.

In the formula (a2-1), Ra²¹ is a lactone-containing cyclic group, a—SO₂-containing cyclic group, or a carbonate-containing cyclic group.

Preferred examples of the lactone-containing cyclic group, the—SO₂-containing cyclic group, and the carbonate-containing cyclic groupin Ra²¹ include the groups represented by the general formulae (a2-r-1)to (a2-r-7), the groups represented by the general formulae (a5-r-1) to(a5-r-4), and the groups represented by the general formulae (ax3-r-1)to (ax3-r-3), respectively.

Above all, the lactone-containing cyclic group or the —SO₂-containingcyclic group is preferable, and the groups represented by each of thegeneral formulae (a2-r-1), (a2-r-2), and (a5-r-1), respectively, aremore preferable. Specifically, any one of the groups represented by thechemical formulae (r-lc-1-1) to (r-lc-1-7), (r-lc-2-1) to (r-lc-2-18),(r-sl-1-1), and (r-sl-1-18) is more preferable.

The constituent unit (a2) which the component (A1) has may be either onekind or two or more kinds.

When the component (A1) has the constituent unit (a2), a proportion ofthe constituent unit (a2) is preferably 1 mol % to 80 mol %, morepreferably 10 mol % to 70 mol %, still more preferably 10 mol % to 65mol %, and especially preferably 10 mol % to 60 mol % relative to atotal sum of all of the constituent units constituting the component(A1).

When the proportion of the constituent unit (a2) is the preferred lowerlimit value or more, the effects due to the fact that the constituentunit (a2) is contained are sufficiently obtained. When the proportion ofthe constituent unit (a2) is not more than the preferred upper limitvalue, a balance with other constituent units can be taken, and variouslithography properties and the pattern shape are enhanced.

Constituent Unit (a3):

The constituent unit (a3) is a constituent unit containing a polargroup-containing aliphatic hydrocarbon group (exclusive of those whichfall within the definition of the constituent unit (a0), (a1-1), (a1-2),or (a2)).

In view of the fact that the component (A1) has the constituent unit(a3), the hydrophilicity of the component (A) increases, resulting incontribution to an enhancement of resolution.

Examples of the polar group include a hydroxyl group, a cyano group, acarboxy group, and a hydroxyalkyl group in which some of hydrogen atomsof an alkyl group are substituted with a fluorine atom, with a hydroxylgroup being especially preferable.

Examples of the aliphatic hydrocarbon group include a linear or branchedhydrocarbon group having 1 to 10 carbon atoms (preferably an alkylenegroup) and a cyclic aliphatic hydrocarbon group (cyclic group). Thecyclic group may be either a monocyclic group or a polycyclic group, andfor example, it can be properly selected and used among a large numberof groups proposed in resins for resist compositions for ArF excimerlasers. The cyclic group is preferably a polycyclic group, and morepreferably a polycyclic group having 7 to 30 carbon atoms.

Above all, a constituent unit derived from an acrylic ester containingan aliphatic polycyclic group containing a hydroxyl group, a cyanogroup, a carboxy group, or a hydroxyalkyl group in which some ofhydrogen atoms of an alkyl group are substituted with a fluorine atom ismore preferable. Examples of the polycyclic group include a group inwhich two or more hydrogen atoms are eliminated from a bicycloalkane, atricycloalkane, a tetracycloalkane, or the like. Specifically, examplesthereof include a group in which two or more hydrogen atoms areeliminated from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane, and tetracyclododecane. Among thesepolycyclic groups, a group in which two or more hydrogen atoms areeliminated from adamantane, a group in which two or more hydrogen atomsare eliminated from norbornane, or a group in which two or more hydrogenatoms are eliminated from tetracyclododecane is preferable from theindustrial standpoint.

As the constituent unit (a3), an arbitrary constituent unit can be usedwithout particular limitations so long as it contains a polargroup-containing aliphatic hydrocarbon group.

The constituent unit (a3) is preferably a constituent unit derived froman acrylic ester in which the hydrogen atom bonded to the carbon atom atthe α-position may be substituted with a substituent, the constituentunit containing a polar group-containing aliphatic hydrocarbon group.

When the hydrocarbon group in the polar group-containing aliphatichydrocarbon group is a linear or branched hydrocarbon group having 1 to10 carbon atoms, the constituent unit (a3) is preferably a constituentunit derived from a hydroxyethyl ester of acrylic acid, and when thehydrocarbon group is a polycyclic group, the constituent unit (a3) ispreferably a constituent unit represented by the following formula(a3-1), a constituent unit represented by the following formula (a3-2),or a constituent unit represented by the following formula (a3-3).

In the formulae, R is the same as that described above; j represents aninteger of 1 to 3; k represents an integer of 1 to 3; t′ represents aninteger of 1 to 3; l represents an integer of 1 to 5; and s representsan integer of 1 to 3.

In the formula (a3-1), j is preferably 1 or 2, and more preferably 1. Inthe case where j is 2, a constituent unit in which the hydroxyl group isbonded to the 3-position and 5-position of the adamantyl group ispreferable. In the case where j is 1, a constituent unit in which thehydroxyl group is bonded to the 3-position of the adamantyl group ispreferable.

j is preferably 1, and a constituent unit in which the hydroxyl group isbonded to the 3-position of the adamantyl group is especiallypreferable.

In the formula (a3-2), k is preferably 1. The cyano group is preferablybonded to the 5-position or 6-position of the norbornyl group.

In the formula (a3-3), t′ is preferably 1. l is preferably 1. s ispreferably 1. In these, it is preferable that the 2-norbornyl group orthe 3-norbornyl group is bonded to the terminal of the carboxy group ofacrylic acid. The fluorinated alkyl alcohol is preferably bonded to the5- or 6-position of the norbornyl group.

The constituent unit (a3) which the component (A1) has may be either onekind or two or more kinds.

In the case where the component (A1) has the constituent unit (a3), aproportion of the constituent unit (a3) is preferably 5 mol % to 50 mol%, more preferably 5 mol % to 40 mol %, and still more preferably 5 mol% to 35 mol % relative to a total sum of all of the constituent unitsconstituting the component (A1).

When the proportion of the constituent unit (a3) is the preferred lowerlimit value or more, the effects due to the fact that the constituentunit (a3) is contained are sufficiently obtained. When the proportion ofthe constituent unit (a3) is not more than the preferred upper limitvalue, a balance with other constituent units is easily taken.

Constituent Unit (a4):

The constituent unit (a4) is a constituent unit containing anacid-nondissociable aliphatic cyclic group.

In view of the fact that the component (A1) has the constituent unit(a4), dry etching resistance of the formed resist pattern is enhanced.In addition, hydrophobicity of the component (A) increases. Inparticular, in the case of a solvent development process, it is thoughtthat the enhancement of hydrophobicity contributes to enhancements inresolution, resist pattern shape, and the like.

The “acid-nondissociable cyclic group” in the constituent unit (a4) is acyclic group which on the occasion of generation of an acid in theresist composition upon exposure (for example, on the occasion ofgeneration of an acid from the component (B) to be described later),even when the acid acts, remains in the constituent unit as it iswithout being dissociated.

The constituent unit (a4) is, for example, preferably a constituent unitderived from an acrylic ester containing an acid-nondissociablealiphatic cyclic group, or the like. As the cyclic group, a large numberof constituent units which have been conventionally known to be used inresin components of resist compositions such as those for ArF excimerlasers and KrF excimer lasers (preferably those for ArF excimer lasers),and the like can be used.

In particular, from the standpoint of easiness in industrialavailability or the like, the constituent unit (a4) is preferably atleast one kind selected from a tricyclodecyl group, an adamantyl group,a tetracyclododecyl group, an isobornyl group, and a norbornyl group.Such a polycyclic group may have a linear or branched alkyl group having1 to 5 carbon atoms as a substituent.

Specifically, examples of the constituent unit (a4) include constituentunits represented by the following general formulae (a4-1) to (a4-7),respectively.

In the formula, R^(α) is the same as that described above.

The constituent unit (a4) which the component (A1) has may be either onekind or two or more kinds.

In the case where the component (A1) has the constituent unit (a4), aproportion of the constituent unit (a4) is preferably 1 mol % to 30 mol%, and more preferably 3 mol % to 20 mol % relative to a total sum ofall of the constituent units constituting the component (A1).

When the proportion of the constituent unit (a4) is the preferred lowerlimit value or more, the effects due to the fact that the constituentunit (a4) is contained are sufficiently obtained, and when theproportion of the constituent unit (a4) is not more than the preferredupper limit value, a balance with other constituent units is easilytaken.

In the resist composition of this aspect, the component (A) contains thehigh-molecular weight compound (A1) having the constituent unit (a0) andthe constituent unit (a1-1).

Specifically, examples of the component (A1) include a high-molecularweight compound composed of a repeating structure of the constituentunit (a0), the constituent unit (a1-1), and the constituent unit (a2),and a high-molecular weight compound composed of a repeating structureof the constituent unit (a0), the constituent unit (a1-1), theconstituent unit (a1-2), and the constituent unit (a2).

A mass average molecular weight (Mw) (as converted into polystyrene bymeans of gel permeation chromatography (GPC)) of the component (A1) isnot particularly limited, but it is preferably 1,000 to 50,000, morepreferably 1,500 to 30,000, and most preferably 2,000 to 20,000.

When the Mw of the component (A1) is not more than the preferred upperlimit value of the foregoing range, sufficient solubility in a resistsolvent for the use as a resist is exhibited, and when it is thepreferred lower limit value of the foregoing range or more, good dryetching resistance is obtained and the resist pattern has a goodcross-sectional shape.

A degree of dispersion (Mw/Mn) of the component (A1) is not particularlylimited, and is preferably 1.0 to 5.0, more preferably 1.0 to 4.0, andmost preferably 1.0 to 3.0. It is to be noted that Mn represents anumber average molecular weight.

The component (A1) may be used alone, or in combination of two or morekinds thereof.

A proportion of the component (A1) in the component (A) is preferably 25mass % or more, more preferably 50 mass % or more, and still morepreferably 75 mass % or more relative to a total mass of the component(A), and it may even be 100 mass %. When the proportion is 25 mass % ormore, a resist pattern which is excellent in various lithographyproperties such as an increase of sensitivity and an improvement ofroughness is easily formed.

In the resist composition of this aspect, regarding the component (A), abase material component (hereinafter, referred to as “component (A2)”)which does not fall under the definition of the component (A1) andexhibits changed solubility in a developing solution by the action of anacid may be used in combination.

The component (A2) is not particularly limited, and may be arbitrarilyselected and used among a large number of components which have beenconventionally known as a base material component for a chemicallyamplified resist composition (for example, base resins such as those forArF excimer lasers and KrF excimer lasers (preferably those for ArFexcimer lasers)). The component (A2) may be used alone, or incombination of two or more kinds thereof.

In the resist composition of this aspect, the component (A) may be usedalone, or in combination of two or more kinds thereof.

In the resist composition of this aspect, the content of the component(A) may be adjusted in conformity with the thickness of the resist filmto be formed, or the like.

Other Components

The resist composition of this aspect preferably further contains anacid generator component (B) which generates an acid upon exposure(hereinafter, referred to as “component (B)”), in addition to theabove-described component (A).

Component (B)

The component (B) is not particularly limited, and those which have beenso far proposed as the acid generator for a chemically amplified resistcan be used.

Examples of such an acid generator include a variety of acid generatorssuch as an onium salt-based acid generator, for example, an iodoniumsalt and a sulfonium salt; an oxime sulfonate-based acid generator; adiazomethane-based acid generator, for example, a bisalkyl or bisarylsulfonyl diazomethane and a poly(bissulfonyl)diazomethane; anitrobenzylsulfonate-based acid generator; an iminosulfonate-based acidgenerator; and a disulfone-based acid generator. Above all, it ispreferable to use an onium salt-based acid generator.

As the onium salt-based acid generator, for example, a compoundrepresented by the following general formula (b-1) (hereinafter, alsoreferred to as “component (b-1)”), a compound represented by a generalformula (b-2) (hereinafter, also referred to as “component (b-2)”), or acompound represented by a general formula (b-3) (hereinafter, alsoreferred to as “component (b-3)”) can be used.

In the formulae, each of R¹⁰¹ and R¹⁰⁴ to R¹⁰⁸ independently representsan optionally substituted cyclic group, an optionally substituted chainalkyl group, or an optionally substituted chain alkenyl group; R¹⁰⁴ andR¹⁰⁵ may be bonded to each other to form a ring; R¹⁰² represents afluorine atom or a fluorinated alkyl group having 1 to 5 carbon atoms;Y¹⁰¹ represents a single bond or a divalent linking group containing anoxygen atom; each of V¹⁰¹ to V¹⁰³ independently represents a singlebond, an alkylene group, or a fluorinated alkylene group; each of L¹⁰¹and L¹⁰² independently represents a single bond or an oxygen atom; eachof L¹⁰³ to L¹⁰⁵ independently represents a single bond, —CO—, or —SO₂—;m represents an integer of 1 or more; and M′^(m+) represents an m-valentonium cation.

Anion Moiety

Anion Moiety of Component (b-1)

In the formula (b-1), R¹⁰¹ represents an optionally substituted cyclicgroup, an optionally substituted chain alkyl group, or an optionallysubstituted chain alkenyl group.

Examples of R¹⁰¹ include the same groups as the optionally substitutedcyclic group, the optionally substituted chain alkyl group, or theoptionally substituted chain alkenyl group in Ra⁰¹ in the formula(a0-1).

Above all, R¹⁰¹ is preferably an optionally substituted cyclic group,and more preferably an optionally substituted cyclic hydrocarbon group.More specifically, a group in which one or more hydrogen atoms areeliminated from a phenyl group, a naphthyl group, or a polycycloalkane,the lactone-containing cyclic groups represented by the formulae(a2-r-1) to (a2-r-7), respectively, and the —SO₂-containing cyclicgroups represented by the general formulae (a5-r-1) to (a5-r-4),respectively are preferable.

In the formula (b-1), Y¹⁰¹ represents a single bond or an oxygenatom-containing divalent linking group.

In the case where Y¹⁰¹ is an oxygen atom-containing divalent linkinggroup, Y¹⁰¹ may contain an atom other than an oxygen atom. Examples ofthe atom other than an oxygen atom include a carbon atom, a hydrogenatom, a sulfur atom, and a nitrogen atom.

Examples of the oxygen atom-containing divalent linking group include anon-hydrocarbon-based oxygen atom-containing linking group such as anoxygen atom (ether bond: —O—), an ester bond (—C(═O)—O—), an oxycarbonylgroup (—O—C(═O)—), an amide bond (—C(═O)—NH—), a carbonyl group(—C(═O)—), and a carbonate bond (—O—C(═O)—O—); and a combination of thenon-hydrocarbon-based oxygen atom-containing linking group with analkylene group. A sulfonyl group (—SO₂—) may be further connected to thecombination. Examples of the combination include linking groupsrepresented by the following formulae (y-al-1) to (y-al-7),respectively.

In the formulae, V′¹⁰¹ represents a single bond or an alkylene grouphaving 1 to 5 carbon atoms; and V′¹⁰² represents a divalent saturatedhydrocarbon group having 1 to 30 carbon atoms.

The divalent saturated hydrocarbon group in V′¹⁰² is preferably analkylene group having 1 to 30 carbon atoms.

The alkylene group in V′¹⁰¹ and V′¹⁰² may be a linear alkylene group, ormay be a branched alkylene group, and it is preferably a linear alkylenegroup.

Specifically, examples of the alkylene group in V′¹⁰¹ and V′¹⁰² includea methylene group [—CH₂—]; an alkylmethylene group such as —CH(CH₃)—,—CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and—C(CH₂CH₃)₂—; an ethylene group [—CH₂CH₂—]; an alkylethylene group suchas —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, and —CH(CH₂CH₃)CH₂—; atrimethylene group (n-propylene group) [—CH₂CH₂CH₂—]; analkyltrimethylene group such as —CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; atetramethylene group [—CH₂CH₂CH₂CH₂—]; an alkyltetramethylene group suchas —CH(CH₃)CH₂CH₂CH₂— and —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylene group[—CH₂CH₂CH₂CH₂CH₂—].

In addition, some of the methylene groups in the above-describedalkylene group in V′¹⁰¹ or V′¹⁰² may be substituted with a divalentaliphatic cyclic group having 5 to 10 carbon atoms. The aliphatic cyclicgroup is preferably a divalent group in which one hydrogen atom isfurther eliminated from the monocyclic or polycyclic aliphatichydrocarbon group in Ra′³ in the formula (a1-r-1), and more preferably acyclohexylene group, a 1,5-adamantylene group, or a 2,6-adamantylenegroup.

Y¹⁰¹ is preferably a divalent linking group containing an ester bond oran ether bond, and the linking groups represented by the formulae(y-al-1) to (y-al-5), respectively are preferable.

In the formula (b-1), V¹⁰¹ represents a single bond, an alkylene group,or a fluorinated alkylene group. The number of carbon atoms of each ofthe alkylene group and the fluorinated alkylene group in V¹⁰¹ ispreferably 1 to 4. Examples of the fluorinated alkylene group in V¹⁰¹include a group in which some or all the hydrogen atoms of the alkylenegroup in V¹⁰¹ are substituted with a fluorine atom. Above all, V¹⁰¹ ispreferably a single bond or a fluorinated alkylene group having 1 to 4carbon atoms.

In the formula (b-1), R¹⁰² represents a fluorine atom or a fluorinatedalkyl group having 1 to 5 carbon atoms. R¹⁰² is preferably a fluorineatom or a perfluoroalkyl group having 1 to 5 carbon atoms, and morepreferably a fluorine atom.

As for specific examples of the anion moiety of the component (b-1), inthe case where Y¹⁰¹ is a single bond, examples thereof include afluorinated alkyl sulfonate anion such as a trifluoromethane sulfonateanion and a perfluorobutane sulfonate anion; and in the case where Y¹⁰¹is an oxygen atom-containing divalent linking group, examples thereofinclude any of anions represented by the following formulae (an-1) to(an-3).

In the formulae, R″¹⁰¹ represents an optionally substituted aliphaticcyclic group, a group represented by each of the formulae (r-hr-1) to(r-hr-6), or an optionally substituted chain alkyl group; R″¹⁰²represents an optionally substituted aliphatic cyclic group, alactone-containing cyclic group represented by each of the formulae(a2-r-1) to (a2-r-7), or an —SO₂-containing cyclic group represented byeach of the formulae (a5-r-1) to (a5-r-4); R″¹⁰³ represents anoptionally substituted aromatic cyclic group, an optionally substitutedaliphatic cyclic group, or an optionally substituted chain alkenylgroup; each v″ independently represents an integer of 0 to 3; each q″independently represents an integer of 1 to 20; t″ represents an integerof 1 to 3; and n″ represents 0 or 1.

The optionally substituted aliphatic cyclic group represented by each ofR″¹⁰¹, R″¹⁰², and R″¹⁰³ is preferably the group exemplified above forthe cyclic aliphatic hydrocarbon group in Ra⁰¹. Examples of thesubstituent include the same substituents as those with which the cyclicaliphatic hydrocarbon group in Ra⁰¹ may be substituted.

The optionally substituted aromatic cyclic group in R″¹⁰³ is preferablythe group exemplified above for the aromatic hydrocarbon group in thecyclic hydrocarbon group in Ra⁰¹ Examples of the substituent include thesame substituents as those with which the aromatic hydrocarbon group inRa⁰¹ may be substituted.

The optionally substituted chain alkyl group in R″¹⁰¹ is preferably thegroup exemplified above for the chain alkyl group in Ra⁰¹. Theoptionally substituted chain alkenyl group in R″¹⁰³ is preferably thegroup exemplified above for the chain alkenyl group in Ra⁰¹.

Anion Moiety of Component (b-2)

In the formula (b-2), each of R¹⁰⁴ and R¹⁰⁵ independently represents anoptionally substituted cyclic group, an optionally substituted chainalkyl group, or an optionally substituted chain alkenyl group, andexamples thereof include the same groups as those in R¹⁰¹ in the formula(b-1). However, R¹⁰⁴ and R¹⁰⁵ may be bonded to each other to form aring.

Each of R¹⁰⁴ and R¹⁰⁵ is preferably an optionally substituted chainalkyl group, and more preferably a linear or branched alkyl group or alinear or branched fluorinated alkyl group.

The number of carbon atoms of the chain alkyl group is preferably 1 to10, more preferably 1 to 7, and still more preferably 1 to 3. The numberof carbon atoms of the chain alkyl group represented by each of R¹⁰⁴ andR¹⁰⁵ is preferably smaller within the above-described range of thenumber of carbon atoms for reasons such as good solubility in a resistsolvent. In addition, in the chain alkyl group represented by each ofR¹⁰⁴ and R¹⁰⁵, the number of the hydrogen atoms substituted with afluorine atom is preferably larger because the strength of the acidincreases, and the transparency to a high energy light or electron beamsof not more than 200 nm is enhanced. A proportion of the fluorine atomin the chain alkyl group, namely a fluorination rate, is preferably 70%to 100%, and more preferably 90% to 100%. A perfluoroalkyl group inwhich all of the hydrogen atoms are substituted with a fluorine atom isthe most preferable.

In the formula (b-2), each of V¹⁰² and V¹⁰³ independently represents asingle bond, an alkylene group, or a fluorinated alkylene group, andexamples thereof include the same groups as those in V¹⁰¹ in the formula(b-1).

In the formula (b-2), each of L¹⁰¹ and L¹⁰² independently represents asingle bond or an oxygen atom.

Anion Moiety of Component (b-3)

In the formula (b-3), each of R¹⁰⁶ to R¹⁰⁸ independently represents anoptionally substituted cyclic group, an optionally substituted chainalkyl group, or an optionally substituted chain alkenyl group, andexamples thereof include the same groups as those in R¹⁰¹ in the formula(b-1).

Each of L¹⁰³ to L¹⁰⁵ independently represents a single bond, —CO—, or—SO₂—.

Cation Moiety

In the formulae (b-1), (b-2), and (b-3), M′^(m+) represents an m-valentonium cation, and preferred examples thereof include a sulfonium cationand an iodonium cation. Specifically, preferred examples of(M′^(m+))_(1/m) include organic cations represented by the followinggeneral formulae (ca-1) to (ca-4), respectively.

In the formulae, each of R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² independentlyrepresents an optionally substituted aryl group, alkyl group or alkenylgroup, and R²⁰¹ to R²⁰³, R²⁰⁶ to R²⁰⁷, or R²¹¹ to R²¹² may be bonded toeach other to form a ring together with a sulfur atom in each formula;each of R²⁰⁸ and R²⁰⁹ independently represents a hydrogen atom or analkyl group having 1 to 5 carbon atoms; R²¹⁰ represents an optionallysubstituted aryl group, alkyl group or alkenyl group, or an—SO₂-containing cyclic group; L²⁰¹ represents —C(═O)— or —C(═O)—O—; eachY²⁰¹ independently represents an arylene group, an alkylene group, or analkenylene group; x represents 1 or 2; and W²⁰¹ represents an(x+1)-valent linking group.

Examples of the aryl group in R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² include anunsubstituted aryl group having 6 to 20 carbon atoms, and the aryl groupis preferably a phenyl group or a naphthyl group.

The alkyl group in R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² is preferably a chain orcyclic alkyl group having 1 to 30 carbon atoms.

The alkenyl group in R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² is preferably analkenyl group having 2 to 10 carbon atoms.

Examples of the substituent which each of R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹²may have include an alkyl group, a halogen atom, a halogenated alkylgroup, a carbonyl group, a cyano group, an amino group, an aryl group,and groups represented by the following formulae (ca-r-1) to (ca-r-7),respectively.

In the formulae, each R′²⁰¹ independently represents a hydrogen atom oran optionally substituted cyclic group, chain alkyl group or chainalkenyl group.

Examples of the optionally substituted cyclic group, the optionallysubstituted chain alkyl group, or the optionally substituted chainalkenyl group represented by R′²⁰¹ include the same groups as those inR¹⁰¹ in the foregoing formula (b-1). Besides, examples of the optionallysubstituted cyclic group or the optionally substituted chain alkyl groupinclude the same acid dissociable group as that represented by theforegoing formula (a1-r-2).

In the case where R²⁰¹ to R²⁰³, R²⁰⁶ to R²⁰⁷, or R²¹¹ to R²¹² may bebonded to each other to form a ring together with a sulfur atom in eachformula, they may be bonded to each other via a hetero atom such as asulfur atom, an oxygen atom, and a nitrogen atom, or a functional groupsuch as a carbonyl group, —SO—, —SO₂—, —SO₃—, —COO—, —CONH—, and—N(R_(N))— (R_(N) represents an alkyl group having 1 to 5 carbon atoms).As for the ring to be formed, one ring containing a sulfur atom in theformula in a ring skeleton thereof is preferably a 3- to 10-memberedring, and especially preferably a 5- to 7-membered ring including thesulfur atom. Specific examples of the ring to be formed include athiophene ring, a thiazole ring, a benzothiophene ring, a thianthrenering, a dibenzothiophene ring, a 9H-thioxanthene ring, a thioxanthonering, a phenoxathiin ring, a tetrahydrothiophenium ring, and atetrahydrothiopyranium ring.

Each of R²⁰⁸ and R²⁰⁹ independently represents a hydrogen atom or analkyl group having 1 to 5 carbon atoms. Of these, a hydrogen atom or analkyl group having 1 to 3 carbon atoms is preferable. In the case whereeach of R²⁰⁸ and R²⁰⁹ is an alkyl group, they may be bonded to eachother to form a ring.

R²¹⁰ represents an optionally substituted aryl group, an optionallysubstituted alkyl group, an optionally substituted alkenyl group, or anoptionally substituted —SO₂-containing cyclic group.

Examples of the aryl group in R²¹⁰ include an unsubstituted aryl grouphaving 6 to 20 carbon atoms. Above all, a phenyl group or a naphthylgroup is preferable.

Examples of the alkyl group in R²¹⁰ preferably include a chain or cyclicalkyl group having 1 to 30 carbon atoms.

The number of carbon atoms of the alkenyl group in R²¹⁰ is preferably 2to 10.

Examples of the optionally substituted —SO₂-containing cyclic group inR²¹⁰ include the same —SO₂-containing cyclic groups as those exemplifiedabove for the “—SO₂-containing cyclic group” represented by Ra²¹ in theforegoing general formula (a2-1). Above all, the group represented bythe foregoing general formula (a5-r-1) is preferable.

Each Y²⁰¹ independently represents an arylene group, an alkylene group,or an alkenylene group.

Examples of the arylene group in Y²⁰¹ include a group in which onehydrogen atom is eliminated from an aryl group exemplified for thearomatic hydrocarbon group in R¹⁰¹ in the foregoing formula (b-1).

Examples of the alkylene group and the alkenylene group in Y²⁰¹ includethe same groups as the aliphatic hydrocarbon groups as the divalenthydrocarbon group in Va¹ in the foregoing general formula (a1-1-1).

In the formula (ca-4), x is 1 or 2.

W²⁰¹ represents an (x+1)-valent (i.e., divalent or trivalent) linkinggroup.

The divalent linking group in W²⁰¹ is preferably an optionallysubstituted divalent hydrocarbon group, and examples thereof include thesame hydrocarbon groups as those exemplified for Ya²¹ in the foregoinggeneral formula (a2-1). The divalent linking group in W²⁰¹ may belinear, branched, or cyclic, and it is preferably cyclic. Above all, agroup in which two carbonyl groups are combined at the both ends of anarylene group is preferable. Examples of the arylene group include aphenylene group and a naphthylene group, with a phenylene group beingespecially preferable.

Examples of the trivalent linking group in W²⁰¹ include a group in whichone hydrogen atom is eliminated from the above-described divalentlinking group in W²⁰¹ and a group in which the above-described divalentlinking group is further bonded to the above-described divalent linkinggroup. The trivalent linking group in W²⁰¹ is preferably a group inwhich two carbonyl groups are bonded to an arylene group.

Specifically, preferred examples of the cation represented by theformula (ca-1) include cations represented by the following formulae(ca-1-1) to (ca-1-67), respectively.

In the formulae, each of g1, g2, and g3 represents a repeating number;g1 represents an integer of 1 to 5; g2 represents an integer of 0 to 20;and g3 represents an integer of 0 to 20.

In the formulae, R″²⁰¹ represents a hydrogen atom or a substituent, andexamples of the substituent include the same substituents as thoseexemplified above for the substituent which each of R²⁰¹ to R²⁰⁷ andR²¹⁰ to R²¹² may have.

Specifically, preferred examples of the cation represented by theformula (ca-2) include a diphenyl iodonium cation and abis(4-tert-butylphenyl)iodonium cation.

Specifically, preferred examples of the cation represented by theformula (ca-3) include cations represented by the following formulae(ca-3-1) to (ca-3-6), respectively.

Specifically, preferred examples of the cation represented by theformula (ca-4) include cations represented by the following formulae(ca-4-1) and (ca-4-2), respectively.

Among the foregoing, the cation moiety [(M′^(m+))_(1/m)] is preferablythe organic cation represented by the general formula (ca-1), and morepreferably the cation represented by each of the formulae (ca-1-1) to(ca-1-67).

As the component (B), the above-described acid generator may be usedalone, or in combination of two or more kinds thereof.

Among the foregoing, as the component (B), an acid generator composed ofa compound represented by the following general formula (b-1-1) isespecially preferably used.

In the formula, R^(101′) represents an optionally substituted cyclicgroup; R¹⁰² represents a fluorine atom or a fluorinated alkyl grouphaving 1 to 5 carbon atoms; Y^(101′) represents a divalent linking groupcontaining an oxygen atom; V¹⁰¹ represents a single bond, an alkylenegroup, or a fluorinated alkylene group; m represents an integer of 1 ormore; and M′^(m+) represents an m-valent onium cation.

In the formula (b-1-1), examples of R^(101′) include the same one as the“optionally substituted cyclic group” in R¹⁰¹, and a cyclic aliphatichydrocarbon group or a heterocyclic group is preferable. Specifically,examples of the heterocyclic group include the lactone-containing cyclicgroups represented by the general formulae (a2-r-1) to (a2-r-7),respectively, the —SO₂-containing cyclic groups represented by thegeneral formulae (a5-1-1) to (a5-r-4), respectively, and theheterocyclic groups represented by the chemical formulae (r-hr-1) to(r-hr-16), respectively.

Examples of Y^(101′) in the formula (b-1-1) include the same one as the“oxygen atom-containing divalent linking group” in Y¹⁰¹ in the formula(b-1).

In the formula (b-1-1), R¹⁰², V¹⁰¹, m, and M′^(m+) are the same as R¹⁰²,V¹⁰¹, m, and M′^(m+) in the formula (b-1).

When the resist composition of this aspect contains the component (B),the content of the component (B) is preferably 0.5 part by mass to 60parts by mass, more preferably 1 part by mass to 50 parts by mass, andstill more preferably 1 part by mass to 40 parts by mass based on 100parts by mass of the component (A).

The content of the component (B) is preferably within the foregoingpreferred range, because the pattern formation is sufficientlyconducted, and on the occasion of dissolving the respective componentsof the resist composition in an organic solvent, a uniform solution isobtained and the storage stability is improved.

Component (D)

The resist composition of this aspect may further contain an aciddiffusion control agent component (hereinafter, referred to as“component (D)”) in addition to the component (A), or in addition to thecomponent (A) and the component (B).

The component (D) acts as a quencher (acid diffusion control agent)which traps an acid generated from the component (B) and the like uponexposure.

The component (D) may be a photodegradable base (D1) which is decomposedupon exposure to lose acid diffusion controlling properties(hereinafter, referred to as “component (D1)”), or a nitrogen-containingorganic compound (D2) which does not fall under the definition of thecomponent (D1) (hereinafter, referred to as “component (D2)”).

Component (D1)

When the resist composition contains the component (D1), a contrastbetween exposed areas and unexposed areas can be enhanced on theoccasion of forming a resist pattern.

Though the component (D1) is not particularly limited so long as it isdecomposed upon exposure to lose acid diffusion controlling properties,the component (D1) is preferably at least one kind of compound selectedfrom the group consisting of a compound represented by the followinggeneral formula (d1-1) (hereinafter, referred to as “component (d1-1)”),a compound represented by the following general formula (d1-2)(hereinafter, referred to as “component (d1-2)”), and a compoundrepresented by the following general formula (d1-3) (hereinafter,referred to as “component (d1-3)”).

Each of the components (d1-1) to (d1-3) does not act as a quencher inexposed areas because it is decomposed to lose acid diffusioncontrolling properties (basicity), but acts as a quencher in unexposedareas.

In the formulae, each of Rd¹ to Rd⁴ represents an optionally substitutedcyclic group, an optionally substituted chain alkyl group, or anoptionally substituted chain alkenyl group, provided that a fluorineatom is not bonded to the carbon atom adjacent to the S atom in Rd² inthe formula (d1-2); Yd¹ represents a single bond or a divalent linkinggroup; m represents an integer of 1 or more, and each M^(m+)independently represents an m-valent organic cation.

Component (d1-1)

Anion Moiety of Component (d1-1):

In the formula (d1-1), Rd¹ represents an optionally substituted cyclicgroup, an optionally substituted chain alkyl group, or an optionallysubstituted chain alkenyl group, and examples thereof include the samegroups as those in R¹⁰¹ in the formula (b-1).

Above all, Rd¹ is preferably an optionally substituted aromatichydrocarbon group, an optionally substituted aliphatic cyclic group, oran optionally substituted chain alkyl group. The substituent which eachof these groups may have is preferably a hydroxyl group, a fluorineatom, or a fluorinated alkyl group.

The aromatic hydrocarbon group is more preferably a phenyl group or anaphthyl group.

The aliphatic cyclic group is more preferably a group in which one ormore hydrogen atoms are eliminated from a polycycloalkane such asadamantane, norbornane, isobornane, tricyclodecane, andtetracyclododecane.

The chain alkyl group is preferably a chain alkyl group having 1 to 10carbon atoms. Specifically, examples thereof include a linear alkylgroup such as a methyl group, an ethyl group, a propyl group, a butylgroup, a pentyl group, a hexyl group, a heptyl group, an octyl group, anonyl group, and a decyl group; and a branched alkyl group such as a1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a2-methylpentyl group, a 3-methylpentyl group, and a 4-methylpentylgroup.

In the case where the chain alkyl group is a fluorinated alkyl grouphaving, as a substituent, a fluorine atom, the number of carbon atoms ofthe fluorinated alkyl group is preferably 1 to 11, more preferably 1 to8, and still more preferably 1 to 4. The fluorinated alkyl group mayalso contain an atom other than a fluorine atom. Examples of the atomother than a fluorine atom include an oxygen atom, a carbon atom, ahydrogen atom, a sulfur atom, and a nitrogen atom.

Rd¹ is preferably a fluorinated alkyl group in which some or allhydrogen atoms constituting a linear alkyl group are substituted with afluorine atom, and more preferably a fluorinated alkyl group (linearperfluoroalkyl group) in which all of hydrogen atoms constituting alinear alkyl group are substituted with a fluorine atom.

Preferred specific examples of the anion moiety of the component (d1-1)are given below.

Cation Moiety of Component (d1-1):

In the formula (d1-1), M^(m+) represents an m-valent organic cation.

Preferred examples of the organic cation represented by M^(m+) includethe same cations as those represented by the general formulae (ca-1) to(ca-4), respectively. Specific examples thereof include cationsrepresented by the formulae (ca-1-1) to (ca-1-67), respectively.

The component (d1-1) may be used alone, or in combination of two or morekinds thereof.

Component (d1-2)

Anion Moiety of Component (d1-2):

In the formula (d1-2), Rd² represents an optionally substituted cyclicgroup, an optionally substituted chain alkyl group, or an optionallysubstituted chain alkenyl group, and examples thereof include the samegroups as those in R¹⁰¹ in the formula (b-1).

However, a fluorine atom is not bonded to (there is nofluorine-substitution at) the carbon atom adjacent to the S atom in Rd².According to this, the anion of the component (d1-2) becomes anappropriately weak acid anion, whereby the quenching ability as thecomponent (D) is enhanced.

Rd² is preferably an optionally substituted aliphatic cyclic group, andmore preferably a (optionally substituted) group in which one or morehydrogen atoms are eliminated from adamantane, norbornane, isobornane,tricyclodecane, tetracyclododecane, or the like; or a group in which oneor more hydrogen atoms are eliminated from camphor or the like.

The hydrocarbon group represented by Rd² may have a substituent.Examples of the substituent include the same groups as those exemplifiedabove for the substituent which the hydrocarbon group (aromatichydrocarbon group or aliphatic hydrocarbon group) in Rd¹ in the formula(d1-1) may have.

Preferred specific examples of the anion moiety of the component (d1-2)are given below.

Cation Moiety of Component (d1-2):

In the formula (d1-2), M^(m+) represents an m-valent organic cation andis the same as M^(m+) in the formula (d1-1).

The component (d1-2) may be used alone, or in combination of two or morekinds thereof.

Component (d1-3)

Anion Moiety of Component (d1-3):

In the formula (d1-3), Rd³ represents an optionally substituted cyclicgroup, an optionally substituted chain alkyl group, or an optionallysubstituted chain alkenyl group, and examples thereof include the samegroups as those in R¹⁰¹ in the formula (b-1). Rd³ is preferably a cyclicgroup, a chain alkyl group, or a chain alkenyl group, each of whichcontains a fluorine atom. Above all, Rd³ is preferably a fluorinatedalkyl group, and more preferably the same fluorinated alkyl group asthat represented by Rd¹ as described above.

In the formula (d1-3), Rd⁴ represents an optionally substituted cyclicgroup, an optionally substituted chain alkyl group, or an optionallysubstituted chain alkenyl group, and examples thereof include the samegroups as those in R¹⁰¹ in the formula (b-1).

Above all, Rd⁴ is preferably an alkyl group, an alkoxy group, an alkenylgroup, or a cyclic group, each of which may have a substituent.

The alkyl group in Rd⁴ is preferably a linear or branched alkyl grouphaving 1 to 5 carbon atoms. Specifically, examples thereof include amethyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group, and a neopentyl group. Some of the hydrogen atoms ofthe alkyl group represented by Rd⁴ may be substituted with a hydroxylgroup, a cyano group, or the like.

The alkoxy group in Rd⁴ is preferably an alkoxy group having 1 to 5carbon atoms. Specifically, examples of the alkoxy group having 1 to 5carbon atoms include a methoxy group, an ethoxy group, an n-propoxygroup, an isopropoxy group, an n-butoxy group, and a tert-butoxy group.Above all, a methoxy group or an ethoxy group is preferable.

Examples of the alkenyl group in Rd⁴ include the same groups as those inR¹⁰¹ in the formula (b-1). Above all, a vinyl group, a propenyl group(allyl group), a 1-methylpropenyl group, and a 2-methylpropenyl groupare preferable. Each of these groups may further have, as a substituent,an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl grouphaving 1 to 5 carbon atoms.

Examples of the cyclic group in Rd⁴ include the same groups as those inR¹⁰¹ in the formula (b-1). Above all, an alicyclic group in which one ormore hydrogen atoms are eliminated from a cycloalkane such ascyclopentane, cyclohexane, adamantane, norbornane, isobornane,tricyclodecane, and tetracyclododecane, or an aromatic group such as aphenyl group and a naphthyl group is preferable. In the case where Rd⁴is an alicyclic group, in view of the fact that the resist compositionis well dissolved in an organic solvent, the lithography properties areenhanced. In addition, in the case where Rd⁴ is an aromatic group, inthe lithography using EUV or the like as an exposure light source, theresist composition exhibits excellent light absorption efficiency, andthe sensitivity and lithography properties are enhanced.

In the formula (d1-3), Yd¹ represents a single bond or a divalentlinking group.

Though the divalent linking group in Yd¹ is not particularly limited,examples thereof include an optionally substituted divalent hydrocarbongroup (aliphatic hydrocarbon group or aromatic hydrocarbon group) and adivalent linking group containing a hetero atom. Examples of each ofthese groups include the same groups as the optionally substituteddivalent hydrocarbon group and the divalent linking group containing ahetero atom exemplified above in the description of the divalent linkinggroup represented by Ya²¹ in the foregoing formula (a2-1).

Yd¹ is preferably a carbonyl group, an ester bond, an amide bond, analkylene group, or a combination thereof. The alkylene group is morepreferably a linear or branched alkylene group, and still morepreferably a methylene group or an ethylene group.

Preferred specific examples of the anion moiety of the component (d1-3)are given below.

Cation Moiety of Component (d1-3):

In the formula (d1-3), M^(m+) represents an m-valent organic cation andis the same as M^(m+) in the formula (d1-1).

The component (d1-3) may be used alone, or in combination of two or morekinds thereof.

As the component (D1), only one kind of the components (d1-1) to (d1-3)may be used, or a combination of two or more kinds thereof may also beused.

The content of the component (D1) is preferably 0.5 part by mass to 10parts by mass, more preferably 0.5 part by mass to 8 parts by mass, andstill more preferably 1 part by mass to 8 parts by mass based on 100parts by mass of the component (A).

When the content of the component (D1) is the preferred lower limitvalue or more, particularly good lithography properties and a goodresist pattern shape are obtained. On the other hand, when it is notmore than the preferred upper limit value, the sensitivity can bemaintained at a satisfactory level, and the throughput is also improved.

Method of Manufacturing Component (D1)

A method of manufacturing the above-described component (d1-1) andcomponent (d1-2) is not particularly limited, and each of the component(d1-1) and the component (d1-2) can be manufactured by a known method.

In addition, a method of manufacturing the component (d1-3) is notparticularly limited, and the component (d1-3) is manufactured in thesame manner as in the method disclosed in, for example, US 20120149916A1.

Component (D2)

As an acid diffusion control agent component, a nitrogen-containingorganic compound component (hereinafter, referred to as “component(D2)”) which does not fall under the definition of the component (D1)may be contained.

The component (D2) is not particularly limited so long as it acts as anacid diffusion control agent and does not fall under the definition ofthe component (D1), and any known compound may be arbitrarily used.Above all, an aliphatic amine, in particular, a secondary aliphaticamine or a tertiary aliphatic amine, is preferable.

The aliphatic amine refers to an amine having one or more aliphaticgroups, and the number of carbon atoms of the aliphatic group ispreferably 1 to 12.

Examples of the aliphatic amine include an amine in which at least oneof hydrogen atoms of ammonia NH₃ is substituted with an alkyl group or ahydroxyalkyl group each having not more than 12 carbon atoms (i.e., analkylamine or an alkyl alcoholamine) and a cyclic amine.

Specific examples of the alkylamine and the alkyl alcoholamine include amonoalkylamine such as n-hexylamine, n-heptylamine, n-octylamine,n-nonylamine, and n-decylamine; a dialkylamine such as diethylamine,di-n-propylamine, di-n-heptylamine, di-n-octylamine, anddicyclohexylamine; a trialkylamine such as trimethylamine,triethylamine, tri-n-propylamine, tri-n-butylamine, tri-n-pentylamine,tri-n-hexylamine, tri-n-heptylamine, tri-n-octylamine, tri-n-nonylamine,tri-n-decylamine, and tri-n-dodecylamine; and an alkyl alcoholamine suchas diethanolamine, triethanolamine, diisopropanolamine,triisopropanolamine, di-n-octanolamine, and tri-n-octanolamine. Ofthese, a trialkylamine having 5 to 10 carbon atoms is more preferable,and tri-n-pentylamine or tri-n-octylamine is especially preferable.

Examples of the cyclic amine include a heterocyclic compound containinga nitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or may be a polycycliccompound (aliphatic polycyclic amine).

Specifically, examples of the aliphatic monocyclic amine includepiperidine and piperazine.

The aliphatic polycyclic amine is preferably an aliphatic polycyclicamine having 6 to 10 carbon atoms. Specifically, examples thereofinclude 1,5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

Examples of other aliphatic amines includetris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine, and triethanolaminetriacetate, with triethanolamine triacetate being preferable.

In addition, an aromatic amine may also be used as the component (D2).

Examples of the aromatic amine include 4-dimethylaminopyridine, pyrrole,indole, pyrazole, imidazole, and derivatives thereof, as well astribenzylamine, 2,6-diisopropylaniline, andN-tert-butoxycarbonylpyrrolidine.

The component (D2) may be used alone, or in combination of two or morekinds thereof.

The component (D2) is generally used in an amount in the range of 0.01part by mass to 5 parts by mass based on 100 parts by mass of thecomponent (A). When the amount of the component (D2) falls within theforegoing range, the resist pattern shape, the post-exposure temporalstability, and the like are enhanced.

When the resist composition of this aspect contains the component (D),among the foregoing, the photodegradable base (D1) which is decomposedupon exposure to lose acid diffusion controlling properties ispreferably contained, and the component (d1-2) is more preferablycontained.

Component (E)

For the purposes of preventing deterioration in sensitivity andenhancing the resist pattern shape, the post-exposure temporalstability, and the like, the resist composition of this aspect cancontain, as an optional component, at least one kind of compound (E)(hereafter, referred to as “component (E)”) selected from the groupconsisting of an organic carboxylic acid and a phosphorus oxo acid and aderivative thereof.

Preferred examples of the organic carboxylic acid include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of the phosphorus oxo acid include phosphoric acid, phosphonicacid, and phosphinic acid, with phosphonic acid being especiallypreferable.

Examples of the phosphorus oxo acid derivative include an ester in whicha hydrogen atom of the above-described oxo acid is substituted with ahydrocarbon group. Examples of the hydrocarbon group include an alkylgroup having 1 to 5 carbon atoms and an aryl group having 6 to 15 carbonatoms.

Examples of the phosphoric acid derivative include a phosphoric acidester such as di-n-butyl phosphate and diphenyl phosphate.

Examples of the phosphonic acid derivative include a phosphonic acidester such as dimethyl phosphonate, di-n-butyl phosphonate,phenylphosphonic acid, diphenyl phosphonate, and dibenzyl phosphonate.

Examples of the phosphinic acid derivative include a phosphinic acidester and phenylphosphinic acid.

The component (E) may be used alone, or in combination of two or morekinds thereof.

In general, the component (E) is used in an amount in the range of 0.01part by mass to 5 parts by mass based on 100 parts by mass of thecomponent (A).

Component (F)

For the purpose of imparting water repellency to the resist film, theresist composition of this aspect may contain a fluorine additive(hereinafter, referred to as “component (F)”).

As the component (F), fluorine-containing high-molecular weightcompounds disclosed in, for example, JP-A-2010-002870, JP-A-2010-032994,JP-A-2010-277043, JP-A-2011-13569, and JP-A-2011-128226 can be used.

More specifically, examples of the component (F) include a polymerhaving a constituent unit (f1) represented by the following formula(f1-1). The polymer is preferably a polymer (homopolymer) composed ofonly the constituent unit (f1) represented by the following formula(f1-1); a copolymer of the constituent unit (f1) and the constituentunit (a1-1); or a copolymer of the constituent unit (f1), a constituentunit derived from acrylic acid or methacrylic acid, and the constituentunit (a1-1). Here, the constituent unit (a1-1) which is copolymerizedwith the constituent unit (f1) is preferably a constituent unit derivedfrom 1-ethyl-1-cyclooctyl(meth)acrylate.

In the formula, R is the same as that described above; each of Rf¹⁰² andRf¹⁰³ independently represents a hydrogen atom, a halogen atom, an alkylgroup having 1 to 5 carbon atoms, or a halogenated alkyl group having 1to 5 carbon atoms, and Rf¹⁰² and Rf¹⁰³ may be the same as or differentfrom each other; nf¹ represents an integer of 1 to 5; and Rf¹⁰¹represents an organic group containing a fluorine atom.

In the formula (f1-1), R which is bonded to the carbon atom at theα-position is the same as that described above. R is preferably ahydrogen atom or a methyl group.

In the formula (f1-1), examples of the halogen atom represented by Rf¹⁰²and Rf¹⁰³ include a fluorine atom, a chlorine atom, a bromine atom, andan iodine atom, with a fluorine atom being especially preferable.Examples of the alkyl group having 1 to 5 carbon atoms, as representedby Rf¹⁰² and Rf¹⁰³, include the same groups as those exemplified abovefor the alkyl group having 1 to 5 carbon atoms, as represented by R. Ofthese, a methyl group or an ethyl group is preferable. Specifically,examples of the halogenated alkyl group having 1 to 5 carbon atoms, asrepresented by Rf¹⁰² and Rf¹⁰³, include a group in which some or all thehydrogen atoms of the above-described alkyl group having 1 to 5 carbonatoms are substituted with a halogen atom. Examples of the halogen atominclude a fluorine atom, a chlorine atom, a bromine atom, and an iodineatom, with a fluorine atom being especially preferable. Above all, asRf¹⁰² and Rf¹⁰³, a hydrogen atom, a fluorine atom, or an alkyl grouphaving 1 to 5 carbon atoms is preferable, and a hydrogen atom, afluorine atom, a methyl group, or an ethyl group is more preferable.

In the formula (f1-1), nf¹ is an integer of 1 to 5, preferably aninteger of 1 to 3, and more preferably 1 or 2.

In the formula (f1-1), Rf¹⁰¹ represents an organic group containing afluorine atom and is preferably a hydrocarbon group containing afluorine atom.

The hydrocarbon group containing a fluorine atom may be linear,branched, or cyclic, and the number of carbon atoms thereof ispreferably 1 to 20, more preferably 1 to 15, and especially preferably 1to 10.

In addition, in the hydrocarbon group containing a fluorine atom, it ispreferable that 25% or more of the hydrogen atoms in the hydrocarbongroup are fluorinated; it is more preferable that 50% or more of thehydrogen atoms in the hydrocarbon group are fluorinated; and, it isespecially preferable that 60% or more of the hydrogen atoms in thehydrocarbon group are fluorinated in view of the fact that thehydrophobicity of the resist film at the time of immersion exposure isincreased.

Above all, Rf¹⁰¹ is especially preferably a fluorinated hydrocarbongroup having 1 to 5 carbon atoms, and most preferably a trifluoromethylgroup, —CH₂—CF₃, —CH₂—CF₂—CF₃, —CH(CF₃)₂, —CH₂—CH₂—CF₃, or—CH₂—CH₂—CF₂—CF₂—CF₂—CF₃.

A mass average molecular weight (Mw) (as converted into standardpolystyrene by means of gel permeation chromatography) of the component(F) is preferably 1,000 to 50,000, more preferably 5,000 to 40,000, andmost preferably 10,000 to 30,000. When the mass average molecular weightof the component (F) is not more than the upper limit value of thisrange, sufficient solubility in a resist solvent for the use as a resistis exhibited, whereas when it is the lower limit value of this range ormore, good dry etching resistance is obtained and the resist pattern hasa good cross-sectional shape.

A degree of dispersion (Mw/Mn) of the component (F) is preferably 1.0 to5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5.

The component (F) may be used alone, or in combination of two or morekinds thereof.

In the case where the component (F) is used, the component (F) ispreferably used in a proportion of 0.5 part by mass to 10 parts by massbased on 100 parts by mass of the component (A).

In the resist composition of this aspect, if desired, miscibleadditives, for example, an additional resin for improving theperformance of the resist film, a dissolution inhibitor, a plasticizer,a stabilizer, a coloring agent, a halation inhibitor, a dye, and thelike can be properly added and contained.

Component (S)

The resist composition of this aspect can be manufactured by dissolvingthe resist materials in an organic solvent (hereafter, sometimesreferred to as “component (S)”).

The component (S) may be any organic solvent so long as it is able todissolve the respective components to be used to give a uniformsolution, and any arbitrary one or two or more kinds of organic solventscan be appropriately selected from those which have been conventionallyknown as solvents for a chemically amplified resist and used.

Examples of the component (S) include a lactone such as γ-butyrolactone;a ketone such as acetone, methyl ethyl ketone (MEK), cyclohexanone,methyl-n-pentyl ketone, methyl isopentyl ketone, and 2-heptanone; apolyhydric alcohol such as ethylene glycol, diethylene glycol, propyleneglycol, and dipropylene glycol; a polyhydric alcohol derivativeincluding a compound having an ester bond, such as ethylene glycolmonoacetate, diethylene glycol monoacetate, propylene glycolmonoacetate, and dipropylene glycol monoacetate, and a compound havingan ether bond, such as a monoalkyl ether, (for example, monomethylether, monoethyl ether, monopropyl ether, or monobutyl ether) ormonophenyl ether of the above-described polyhydric alcohol or theabove-described compound having an ester bond [of these, propyleneglycol monomethyl ether acetate (PGMEA) or propylene glycol monomethylether (PGME) is preferable]; a cyclic ether such as dioxane; an estersuch as methyl lactate, ethyl lactate (EL), methyl acetate, ethylacetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; an aromatic organicsolvent such as anisole, ethyl benzyl ether, cresyl methyl ether,diphenyl ether, dibenzyl ether, phenetole, butyl phenyl ether,ethylbenzene, diethylbenzene, pentylbenzene, isopropylbenzene, toluene,xylene, cymene, and mesitylene; and dimethyl sulfoxide (DMSO).

These organic solvents may be used alone, or as a mixed solvent of twoor more kinds thereof.

Above all, PGMEA, PGME, γ-butyrolactone, EL, or cyclohexanone ispreferable.

In addition, a mixed solvent obtained by mixing PGMEA with a polarsolvent is also preferable. Though a blending ratio (mass ratio) of themixed solvent may be appropriately determined while taking intoconsideration the compatibility of PGMEA with the polar solvent or thelike, it is preferable to allow the blending ratio to fall within therange of 1:9 to 9:1, and more preferably 2:8 to 8:2.

More specifically, in the case where EL or cyclohexanone is blended asthe polar solvent, a mass ratio of PGMEA to EL or cyclohexanone ispreferably 1:9 to 9:1, and more preferably 2:8 to 8:2. In addition, inthe case where PGME is blended as the polar solvent, amass ratio ofPGMEA to PGME is preferably 1:9 to 9:1, more preferably 2:8 to 8:2, andstill more preferably 3:7 to 7:3. Furthermore, a mixed solvent of PGMEA,PGME, and cyclohexanone is also preferable.

In addition, as the component (S), besides, a mixed solvent of at leastone kind selected from PGMEA and EL with γ-butyrolactone is alsopreferable. In that case, a mixing proportion is preferably 70:30 to95:5 in terms of a mass ratio of the former to the latter.

The amount of the component (S) used is not particularly limited, and itis properly set in a concentration at which coating on a substrate orthe like can be conducted, according to the thickness of the coatingfilm. In general, the component (S) is used such that the solid contentconcentration of the resist composition falls within the range of 1 mass% to 20 mass %, and preferably 2 mass % to 15 mass %.

According to the resist composition of the invention, a resist patternwhich is excellent in various lithography properties can be formed.

With an advance in lithography techniques, expansion of applicationfields thereof, and the like, enhancements of various lithographyproperties such as an increase of sensitivity and an improvement ofroughness are required. In general, from the viewpoint of a balance invarious lithography properties, plural kinds of constituent units areused in a base resin which has been used in a chemically amplifiedresist composition. However, for example, although introducing amonocyclic group-containing acid decomposable group to the base resin iseffective to improve the roughness, the thickness (pattern height) of aresist pattern tends to easily decrease due to development, compared tothat before the development, and thus a problem occurs in the formationof a fine pattern. As described above, in the formation of a finepattern, it is difficult to balance a plurality of lithographyproperties with each other.

According to the invention, when the high-molecular weight compound (A1)in which the constituent unit (a0) represented by the general formula(a0-1) and the constituent unit (a1-1) including a monocyclicgroup-containing acid decomposable group whose polarity increases by theaction of an acid are combined is used as the base resin of the resistcomposition, required sensitivity and lithography properties such as animprovement of roughness and a pattern height can be satisfied in abalanced manner in the formation of a resist pattern.

Resist Pattern Forming Method

A resist pattern forming method of a second aspect of the inventionincludes a step of forming a resist film on a support using a resistcomposition of the first aspect of the invention, a step of exposing theresist film, and a step of developing the resist film after the exposureto form a resist pattern.

For example, the resist pattern forming method of this aspect can beperformed as follows.

First, the resist composition according to the first aspect is appliedto a support using a spinner or the like, and a baking (post-applybaking (PAB)) treatment is conducted under a temperature condition of,for example, 80° C. to 150° C. for 40 to 120 seconds, and preferably 60to 90 seconds, thereby forming a resist film.

Subsequently, using an exposure apparatus, for example, an ArF exposureapparatus, an electron beam drawing apparatus, or an EUV exposureapparatus, the resist film is exposed through a mask having apredetermined pattern formed thereon (mask pattern) or selectivelyexposed without using a mask pattern by drawing by means of directirradiation with electron beams, or the like. Then, a baking(post-exposure baking (PEB)) treatment is conducted under a temperaturecondition of, for example, 80° C. to 150° C. for 40 to 120 seconds, andpreferably 60 to 90 seconds.

Subsequently, the resist film is subjected to a development treatment.In the case of an alkali development process, an alkali developingsolution is used to perform the development treatment, and in the caseof a solvent development process, a developing solution containing anorganic solvent (organic developing solution) is used to perform thedevelopment treatment.

After the development treatment, a rinse treatment is preferablyperformed. In the rinse treatment, in the case of an alkali developmentprocess, water rinsing using pure water is preferable, and in the caseof a solvent development process, a rinse solution containing an organicsolvent is preferably used.

In the case of the solvent development process, after the developmenttreatment or the rinse treatment, a treatment of removing the developingsolution or rinse solution deposited on the pattern with a supercriticalfluid may be conducted.

After the development treatment or the rinse treatment, drying isperformed. In some cases, a baking treatment (post-baking) may beconducted after the development treatment. In this manner, a resistpattern can be obtained.

The support is not particularly limited, and a conventionally knownsupport can be used. For example, substrates for electronic components,and such substrates having a predetermined wiring pattern formed thereoncan be exemplified. More specifically, examples thereof include ametal-made substrate such as silicon wafer, copper, chromium, iron, andaluminum, and a glass substrate. As a material for the wiring pattern,for example, copper, aluminum, nickel, or gold can be used.

In addition, as the support, a support in which an inorganic and/ororganic film is provided on the above-described substrate may also beused. Examples of the inorganic film include an inorganic antireflectionfilm (inorganic BARC). Examples of the organic film include an organicfilm such as an organic antireflection film (organic BARC) and a lowerlayer organic film in the multilayer resist method.

Here, the multilayer resist method is a method in which at least onelayer of an organic film (lower layer organic film) and at least onelayer of a resist film (upper layer resist film) are provided on asubstrate, and the lower layer organic film is subjected to patterningwhile using, as a mask, a resist pattern formed on the upper layerresist film, and it is said that a pattern with a high aspect ratio canbe formed. That is, according to the multilayer resist method, since arequired thickness can be ensured by the lower layer organic film, theresist film can be made thin, so that it becomes possible to form a finepattern with a high aspect ratio.

Basically, the multilayer resist method is classified into a method offorming a double-layer structure of an upper layer resist film and alower layer organic film (double-layer resist method), and a method offorming a multilayer structure of three or more layers, in which one ormore interlayers (for example, a thin metal film) are provided betweenan upper layer resist film and a lower layer organic film (triple-layerresist method).

The wavelength to be used for the exposure is not particularly limited,and the exposure can be conducted using radiation such as ArF excimerlasers, KrF excimer lasers, F₂ excimer lasers, extreme ultraviolet rays(EUV), vacuum ultraviolet rays (VUV), electron beams (EB), X rays, andsoft X rays. The resist composition is high in usefulness for KrFexcimer lasers, ArF excimer lasers, EB, or EUV, and is especially usefulfor ArF excimer lasers, EB, or EUV.

The method of exposing the resist film may be conducted by means ofgeneral exposure (dry exposure) which is conducted in air or an inertgas such as nitrogen, or it may be conducted by means of liquidimmersion lithography.

The liquid immersion lithography is an exposure method in which a regionbetween a resist film and a lens located at the lowermost position of anexposure apparatus is filled in advance with a solvent (liquid immersionmedium) having a refractive index larger than a refractive index of air,and the exposure (immersion exposure) is conducted in that state.

The immersion medium is preferably a solvent having a refractive indexlarger than a refractive index of air and smaller than a refractiveindex of a resist film to be exposed. The refractive index of such asolvent is not particularly limited so long as it falls within theforegoing range.

Examples of the solvent having a refractive index larger than arefractive index of air and smaller than a refractive index of theresist film include water, a fluorine-based inert liquid, asilicon-based solvent, and a hydrocarbon-based solvent.

Specific examples of the fluorine-based inert liquid include a liquidcomposed mainly of a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅, and C₅H₃F₇. Of these, fluorine-based inert liquids having aboiling point of 70° C. to 180° C. are preferable, and those having aboiling point of 80° C. to 160° C. are more preferable. A fluorine-basedinert liquid having a boiling point falling within the foregoing rangeis preferable because after completion of the exposure, the removal ofthe medium used for the liquid immersion can be conducted by a simplemethod.

As the fluorine-based inert liquid, in particular, a perfluoroalkylcompound in which all of hydrogen atoms of an alkyl group aresubstituted with a fluorine atom is preferable. Specifically, examplesof the perfluoroalkyl compound include a perfluoroalkylether compoundand a perfluoroalkylamine compound.

Furthermore, specifically, examples of the perfluoroalkylether compoundinclude perfluoro(2-butyl-tetrahydrofuran) (boiling point: 102° C.), andexamples of the perfluoroalkylamine compound includeperfluorotributylamine (boiling point: 174° C.).

As the liquid immersion medium, water is preferably used from theviewpoints of cost, safety, environmental issue, and versatility.

Examples of the alkali development solution used in the developmenttreatment in the alkali development process include a 0.1 mass % to 10mass % aqueous solution of tetramethylammonium hydroxide (TMAH).

The organic solvent which is contained in an organic developing solutionused in the development treatment in the solvent development process maybe an organic solvent capable of dissolving the component (A) (component(A) before the exposure) therein, and it can be properly selected amongknown organic solvents. Specifically, examples thereof include ahydrocarbon-based solvent and a polar solvent such as a ketone-basedsolvent, an ester-based solvent, an alcohol-based solvent, anitrile-based solvent, an amide-based solvent, and an ether-basedsolvent.

The ketone-based solvent is an organic solvent containing C≡C(═O)—C in astructure thereof. The ester-based solvent is an organic solventcontaining C≡C(═O)—O—C in a structure thereof. The alcohol-based solventis an organic solvent containing an alcoholic hydroxyl group in astructure thereof, and the term “alcoholic hydroxyl group” means ahydroxyl group bonded to a carbon atom of an aliphatic hydrocarbongroup. The nitrile-based solvent is an organic solvent containing anitrile group in a structure thereof. The amide-based solvent is anorganic solvent containing an amide group in a structure thereof. Theether-based solvent is an organic solvent containing C—O—C in astructure thereof.

Among organic solvents, there is also present an organic solventcontaining plural kinds of functional groups which characterize theabove-described respective solvents, in a structure thereof. In thatcase, the organic solvent is thought to fall under the definition of anysolvent species containing a functional group which this organic solventhas. For example, diethylene glycol monomethyl ether falls under thedefinition of any of the alcohol-based solvent or the ether-basedsolvent in the above-described classification.

The hydrocarbon-based solvent is a hydrocarbon solvent which is composedof a hydrocarbon which may be halogenated and does not have asubstituent other than the halogen atom. Examples of the halogen atominclude a fluorine atom, a chlorine atom, a bromine atom, and an iodineatom, with a fluorine atom being preferable.

Above all, the organic solvent which is contained in an organicdeveloping solution is preferably a polar solvent, and preferredexamples thereof include a ketone-based solvent, an ester-based solvent,and a nitrile-based solvent.

Specific examples of the ketone-based solvent include 1-octanone,2-octanone, 1-nonanone, 2-nonanone, acetone, 4-heptanone, 1-hexanone,2-hexanone, diisobutyl ketone, cyclohexanone, methylcyclohexanone,phenylacetone, methyl ethyl ketone, methyl isobutyl ketone,acetylacetone, acetonylacetone, ionone, diacetonyl alcohol, acetylcarbinol, acetophenone, methyl naphthyl ketone, isophorone, propylenecarbonate, γ-butyrolactone, and methyl amyl ketone (2-heptanone).

The ketone-based solvent is preferably methyl amyl ketone (2-heptanone).

Examples of the ester-based solvent include methyl acetate, butylacetate, ethyl acetate, isopropyl acetate, amyl acetate, isoamylacetate, ethyl methoxyacetate, ethyl ethoxyacetate, propylene glycolmonomethyl ether acetate, ethylene glycol monoethyl ether acetate,ethylene glycol monopropyl ether acetate, ethylene glycol monobutylether acetate, ethylene glycol monophenyl ether acetate, diethyleneglycol monomethyl ether acetate, diethylene glycol monopropyl etheracetate, diethylene glycol monoethyl ether acetate, diethylene glycolmonophenyl ether acetate, diethylene glycol monobutyl ether acetate,2-methoxybutyl acetate, 3-methoxybutyl acetate, 4-methoxybutyl acetate,3-methyl-3-methoxybutyl acetate, 3-ethyl-3-methoxybutyl acetate,propylene glycol monomethyl ether acetate, propylene glycol monoethylether acetate, propylene glycol monopropyl ether acetate, 2-ethoxybutylacetate, 4-ethoxybutyl acetate, 4-propoxybutyl acetate, 2-methoxypentylacetate, 3-methoxypentyl acetate, 4-methoxypentyl acetate,2-methyl-3-methoxypentyl acetate, 3-methyl-3-methoxypentyl acetate,3-methyl-4-methoxypentyl acetate, 4-methyl-4-methoxypentyl acetate,propylene glycol diacetate, methyl formate, ethyl formate, butylformate, propyl formate, ethyl lactate, butyl lactate, propyl lactate,ethyl carbonate, propyl carbonate, butyl carbonate, methyl pyruvate,ethyl pyruvate, propyl pyruvate, butyl pyruvate, methyl acetoacetate,ethyl acetoacetate, methyl propionate, ethyl propionate, propylpropionate, isopropyl propionate, methyl 2-hydroxypropionate, ethyl2-hydroxypropionate, methyl 3-methoxypropionate, ethyl3-methoxypropionate, ethyl 3-ethoxypropionate, and propyl3-methoxypropionate.

The ester-based solvent is preferably butyl acetate.

Examples of the nitrile-based solvent include acetonitrile,propionitrile, valeronitrile, and butyronitrile.

If desired, the organic developing solution can be blended with a knownadditive. Examples of the additive include a surfactant. Though thesurfactant is not particularly limited, for example, an ionic ornonionic fluorine-based and/or silicon-based surfactant can be used. Thesurfactant is preferably a nonionic surfactant, and is more preferably afluorine-based surfactant or a silicon-based surfactant.

In the case of blending the surfactant, the blending amount thereof isusually 0.001 mass % to 5 mass %, preferably 0.005 mass % to 2 mass %,and more preferably 0.01 mass % to 0.5 mass % relative to the wholeamount of the organic developing solution.

It is possible to carry out the development treatment through a knowndevelopment method. Examples of the development treatment include amethod of immersing a support in a developing solution for a certainperiod of time (dip method); a method of raising a developing solutionon the surface of a support due to a surface tension and making itstationary for a certain period of time (puddle method); a method ofspraying a developing solution onto the surface of a support (spraymethod); and a method of continuously dispensing a developing solutiononto a support rotating at a fixed rate while scanning a developingsolution dispense nozzle at a fixed rate (dynamic dispense method).

As the organic solvent contained in the rinse solution which is used inthe rinse treatment after the development treatment in the solventdevelopment process, among the organic solvents exemplified above forthe organic solvent which is used in the organic developing solution, anorganic solvent which hardly dissolves the resist pattern can beproperly selected and used. In general, at least one kind of solventselected from a hydrocarbon-based solvent, a ketone-based solvent, anester-based solvent, an alcohol-based solvent, an amide-based solvent,and an ether-based solvent is used. Of these, at least one kind selectedfrom a hydrocarbon-based solvent, a ketone-based solvent, an ester-basedsolvent, an alcohol-based solvent, and an amide-based solvent ispreferable; at least one kind selected from an alcohol-based solvent andan ester-based solvent is more preferable; and an alcohol-based solventis especially preferable.

The alcohol-based solvent which is used in the rinse solution ispreferably a monohydric alcohol having 6 to 8 carbon atoms, and themonohydric alcohol may be linear, branched, or cyclic. Specifically,examples thereof include 1-hexanol, 1-heptanol, 1-octanol, 2-hexanol,2-heptanol, 2-octanol, 3-hexanol, 3-heptanol, 3-octanol, 4-octanol, andbenzyl alcohol. Of these, 1-hexanol, 2-heptanol, or 2-hexanol ispreferable, and 1-hexanol or 2-hexanol is more preferable.

These organic solvents may be used alone, or as a mixture of two or morekinds thereof. In addition, such an organic solvent may be mixed with anorganic solvent other than the foregoing organic solvents or water andused. However, taking into consideration the development properties, anamount of water blended in the rinse solution is preferably not morethan 30 mass %, more preferably not more than 10 mass %, still morepreferably not more than 5 mass %, and especially preferably not morethan 3 mass % relative to the whole amount of the rinse solution.

The rinse solution can be blended with a known additive, if desired.Examples of the additive include a surfactant. Examples of thesurfactant include the same surfactants as those described above. Aboveall, a nonionic surfactant is preferable, and a fluorine-basedsurfactant or a silicon-based surfactant is more preferable.

In the case of blending the surfactant, the blending amount thereof isusually 0.001 mass % to 5 mass %, preferably 0.005 mass % to 2 mass %,and more preferably 0.01 mass % to 0.5 mass % relative to the wholeamount of the rinse solution.

The rinse treatment (washing treatment) using a rinse solution can becarried out through a known rinse method. Examples of the method includea method of continuously dispensing a rinse solution onto a supportrotating at a fixed rate (rotary coating method); a method of immersinga support in a rinse solution for a certain period of time (dip method);and a method of spraying a rinse solution onto the surface of a support(spray method).

EXAMPLES

The invention is hereunder described in more detail by reference to thefollowing Examples, but it should not be construed that the invention islimited to these Examples.

In Examples, a compound represented by a chemical formula (1) isdesignated as “compound (1)”, and the same applies for compoundsrepresented by other chemical formulae.

Examples of Manufacturing of High-Molecular Weight Compound

In Examples, to obtain a high-molecular weight compound used as a basematerial component, compounds as monomers represented by the followingchemical formulae were used in combination in a predetermined molarratio and copolymerized through a known radical polymerization method.

High-Molecular Weight Compounds 1 to 19

Regarding obtained high-molecular weight compounds 1 to 19, a monomercomposition ratio of the high-molecular weight compound obtained bymeans of ¹³C-NMR (a proportion (molar ratio) of each constituent unit ina structure), a mass average molecular weight (Mw) as converted intostandard polystyrene obtained through GPC measurement, and a degree ofmolecular weight dispersion (Mw/Mn) are recorded together in Table 1.

TABLE 1 High- molecular weight Compound (molar ratio) compound (21)(111) (112) (113) (114) (01) (02) (03) (04) (31) (121) Mw Mw/Mn 1 45 3520 6800 1.6 2 45 35 20 6500 1.6 3 50 30 20 6600 1.6 4 50 40 10 6900 1.65 50 35 15 6800 1.6 6 50 35 15 6800 1.6 7 40 35 25 6800 1.6 8 45  5 2030 6900 1.6 9 50 40 10 6900 1.6 10 50 40 10 6900 1.6 11 50 40 10 69001.6 12 35 35 30 6900 1.6 13 30 35 35 6900 1.6 14 25 35 40 6900 1.6 15 4535 20 7000 1.6 16 45 35 20 6900 1.6 17 45 35 20 6900 1.6 18 50 50 69001.6 19 45 20 35 6900 1.6

Preparation of Resist Composition Examples 1 to 16 and ComparativeExamples 1 to 3

A resist composition of each of Examples and Comparative Examples wasprepared by mixing and dissolving the respective components shown inTable 2.

TABLE 2 Com- Com- Com- Component Component ponent ponent ponent (A) (B)(D) (F) (S) Example 1 (A)-1 (B)-1 (D)-1 (F)-1 (S)-1 [100] [14.0] [6.9][3.0] [3200] Example 2 (A)-2 (B)-1 (D)-1 (F)-1 (S)-1 [100] [14.0] [6.9][3.0] [3200] Example 3 (A)-3 (B)-1 (D)-1 (F)-1 (S)-1 [100] [14.0] [6.9][3.0] [3200] Example 4 (A)-4 (B)-1 (D)-1 (F)-1 (S)-1 [100] [14.0] [6.9][3.0] [3200] Example 5 (A)-5 (B)-1 (D)-1 (F)-1 (S)-1 [100] [14.0] [6.9][3.0] [3200] Example 6 (A)-6 (B)-1 (D)-1 (F)-1 (S)-1 [100] [14.0] [6.9][3.0] [3200] Example 7 (A)-7 (B)-1 (D)-1 (F)-1 (S)-1 [100] [14.0] [6.9][3.0] [3200] Example 8 (A)-8 (B)-1 (D)-1 (F)-1 (S)-1 [100] [14.0] [6.9][3.0] [3200] Example 9 (A)-9 (B)-1 (D)-1 (F)-1 (S)-1 [100] [14.0] [6.9][3.0] [3200] Example 10 (A)-10 (B)-1 (D)-1 (F)-1 (S)-1 [100] [14.0][6.9] [3.0] [3200] Example 11 (A)-11 (B)-1 (D)-1 (F)-1 (S)-1 [100][14.0] [6.9] [3.0] [3200] Example 12 (A)-12 (B)-1 (D)-1 (F)-1 (S)-1[100] [14.0] [6.9] [3.0] [3200] Example 13 (A)-13 (B)-1 (D)-1 (F)-1(S)-1 [100] [14.0] [6.9] [3.0] [3200] Example 14 (A)-14 (B)-1 (D)-1(F)-1 (S)-1 [100] [14.0] [6.9] [3.0] [3200] Example 15 (A)-15 (B)-1(D)-1 (F)-1 (S)-1 [100] [14.0] [6.9] [3.0] [3200] Example 16 (A)-16(B)-1 (D)-1 (F)-1 (S)-1 [100] [14.0] [6.9] [3.0] [3200] Comparative(A)-17 (B)-1 (D)-1 (F)-1 (S)-1 Example 1 [100] [14.0] [6.9] [3.0] [3200]Comparative (A)-18 (B)-1 (D)-1 (F)-1 (S)-1 Example 2 [100] [14.0] [6.9][3.0] [3200] Comparative (A)-19 (B)-1 (D)-1 (F)-1 (S)-1 Example 3 [100][14.0] [6.9] [3.0] [3200]

In Table 2, the respective symbols have the following meanings. Thenumerical values in the square brackets represent a blending amount(parts by mass).

(A)-1 to (A)-19: The above-described high-molecular weight compounds 1to 19.

(B)-1: An acid generator formed of a compound represented by thefollowing chemical formula (B)-1.

(D)-1: A photodegradable base composed of a compound represented by thefollowing chemical formula (D)-1.

(F)-1: A fluorine-containing high-molecular weight compound representedby the following chemical formula (F)-1. A mass average molecular weight(Mw) as converted into standard polystyrene obtained through GPCmeasurement is 25,000, and a degree of molecular weight dispersion(Mw/Mn) is 2.0.

(S)-1: A mixed solvent of propylene glycol monomethyl etheracetate/propylene glycol monomethyl ether/cyclohexanone=45/30/25 (massratio).

Using the obtained resist compositions, resist patterns were formed, andsensitivity, line wise roughness (LWR), and a pattern height thereofwere evaluated as follows.

Formation of Resist Pattern

An organic antireflection film composition “ARC95” (product name,manufactured by Brewer Science Ltd.) was applied onto an 12-inch siliconwafer using a spinner, and the composition was then baked and dried at205° C. for 60 seconds on a hotplate, thereby forming an organicantireflection film having a thickness of 90 nm.

Then, each of the resist compositions of Examples and ComparativeExamples was applied onto the organic antireflection film using aspinner, and was then prebaked (PAB) and dried on a hotplate at atemperature of 110° C. for 60 seconds, thereby forming a resist filmhaving a thickness of 90 nm.

Subsequently, using an ArF exposure apparatus for liquid immersion,NSR-S609B (manufactured by Nikon Corporation; numerical aperture(NA)=1.07, Dipole 0.97/0.78 with polano, liquid immersion medium:water), the resist film was selectively irradiated with ArF excimerlasers (193 nm) through a binary mask.

Thereafter, a post-exposure baking (PEB) treatment was conducted at atemperature of 95° C. for 60 seconds.

Next, alkali development was performed for 10 seconds at 23° C. in a2.38 mass % aqueous solution of TMAH (product name: NMD-3, manufacturedby Tokyo Ohka Kogyo Co., Ltd.), and then the resist film waswater-rinsed for 30 seconds using pure water, followed by drying byshaking.

As a result, in each of Examples and Comparative Examples, a 1:1line-and-space (LS) pattern having a line width of 50 nm and a pitch of100 nm was formed.

In the formation of the resist pattern in each of Examples andComparative Examples, an optimum exposure amount (sensitivity) Eop(mJ/cm²) at which the LS pattern was formed was determined. The resultsare shown in Table 3.

Evaluation of Line Wise Roughness (LWR)

In the LS pattern formed through the above-described “formation ofresist pattern”, a space width was measured at 400 places in alongitudinal direction of the space using a measuring scanning electronmicroscope (SEM) (accelerating voltage: 300 V, product name: S-9380,manufactured by Hitachi High-Technologies Corporation). From the resultsthereof, a value (3 s) three times larger than a standard deviation (s)was obtained, and an average value (nm) of 3 s at 400 places wascalculated as a measure of LWR. The results thereof are shown in Table3.

The smaller the value of 3 s, the less the roughness of the line width,and it means that a LS pattern having a more uniform width is obtained.

Evaluation of Pattern Height

The height (nm) of the LS pattern formed through the above-described“formation of resist pattern” was measured using a wafershape/characteristic measurement apparatus (product name: SCD-XT,manufactured by KLA-TENCOR Corporation).

Based on the result, a proportion (%) of the height of the LS patternafter development to the thickness (90 nm) of the resist film beforedevelopment was obtained. The result is shown as “pattern height (%)” inTable 3.

TABLE 3 Eop LWR Pattern (mJ/cm²) (nm) Height (%) Example 1 14 3.3 94Example 2 14 3.2 95 Example 3 14 3.1 94 Example 4 14 3.2 93 Example 5 143.1 95 Example 6 14 3.3 95 Example 7 14 3.2 94 Example 8 19 3.4 94Example 9 21 3.3 95 Example 10 12 3.3 94 Example 11 20 3.2 94 Example 1214 3.9 93 Example 13 13 3.9 93 Example 14 12 4.0 92 Example 15 14 3.4 92Example 16 13 3.5 90 Comparative 22 3.2 93 Example 1 Comparative 20 3.285 Example 2 Comparative 25 4.1 92 Example 3

From the results shown in Table 3, it is possible to confirm that theresist compositions of Examples 1 to 16 to which the invention isapplied exhibits high sensitivity compared to the resist composition ofComparative Example 1, secures a pattern height compared to the resistcomposition of Comparative Example 2, and has decreased roughness, andthus has high sensitivity compared to the resist composition ofComparative Example 3.

That is, when the invention is applied, it is possible to form a resistpattern which is excellent in various lithography properties.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

What is claimed is:
 1. A resist composition which generates an acid uponexposure and exhibits changed solubility in a developing solution by theaction of the acid, comprising: a base material component (A) whichexhibits changed solubility in a developing solution by the action of anacid, wherein the base material component (A) contains a high-molecularweight compound (A1) having a constituent unit (a0) represented by thefollowing general formula (a0-1) and a constituent unit (a1-1) includinga monocyclic group-containing acid decomposable group whose polarityincreases by the action of an acid:

wherein R represents a hydrogen atom, an alkyl group having 1 to 5carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms;Ya01 represents a single bond or a divalent linking group; X01represents a sulfur atom or an oxygen atom; and Ra01 represents anoptionally substituted polycyclic group, or an optionally substitutedchain alkenyl group.
 2. The resist composition according to claim 1,wherein a proportion of the constituent unit (a0) is 35 mol % or lessrelative to a total sum of all of constituent units constituting thehigh-molecular weight compound (A1).
 3. The resist composition accordingto claim 1, further comprising: an acid generator component (B) whichgenerates an acid upon exposure.
 4. The resist composition according toclaim 3, further comprising: a photodegradable base (D1) which isdecomposed upon exposure to lose acid diffusion controlling properties.5. A resist pattern forming method comprising: forming a resist film ona support using the resist composition according to claim 1; exposingthe resist film; and developing the resist film after the exposure toform a resist pattern.